US3515026A - Chord zither with tubular frame - Google Patents

Description

June 2, 1970 J. R. ROHRBQUGH CHORD ZITHER WITH TUBULAR FRAME 3 Sheets-Sheet 1 Filed Aug. 19, 1968 ,rwE/vme. Clo/{M J9. fla /260061,;

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J. R. ROHRBOUGH CHORD ZITHER WITH TUBULAR FRAME June 2, 1970 3 Sheets-Sheet 2 Filed Aug. 19, 1968 4 jWE-MIbE. claw M J9. 30%?8006/4 J. R. ROHRBOUGH CHORD ZITHER WITH TUBULAR FRAME June 2, 1970 3 Sheets-Sheet 5 Filed Aug. 19, 1968 United States Patent Int. Cl. Gd 1/12 US. Cl. 84-286 10 Claims ABSTRACT OF THE DISCLOSURE A chord zither combining a wooden sound box with a tubular metal frame, the strings being anchored to and tensioned through the latter. In the preferred form, the chord bars are retained in an interchangeable magazine, which is slideably movable over said strings within a bridge structure which may be mounted on said sound box, but must be supported (directly or indirectly) by adjacent parts of the metal frame. The upper part of said bridge structure is a key table in which are mounted keys for operating the chord bars contained within the chord bar magazine, each chord bar being slideable under the corresponding key to permit operation for all positions of said magazine within the bridge structure.

This invention relates generally to chord zithers of the type in which string fingering is achieved by means of several bars movably mounted over the strings for selective damping of a particular set of strings when a corresponding bar is pressed by the player. More particularly, the present invention is a chord zither in which the sound box is of uniquely light construction, but is enclosed within a metal outer frame which absorbs the string tension and also provides the structural strength to support a bridge structure over the strings, in which structure several unique chord bar systems can be accommodated.

Chord zithers are widely used for instructional purposes in the public schools. In addition, they have achieved wide spread popularity among both amateur and professional musicians because of the ease with which a player can learn to produce a wide range of enjoyable music.

The classical zither, known for centuries, is very diflficult to play, because of the manual fingering of the strings, and has been mastered by only a relatively few expert musicians. In the chord zither, however, no string fingering skill is required, since string fingering is accomplished mechanically by the use of chord bars. These bars, very commonly fifteen or sixteen in number, are resiliently supported above the strings and transversely to them. The underside of each bar is provided with a number of felt damping pads; these are spaced differently for each of the chord bars. The top of each chord bar is provided with a push button, or the like, suitably identified by letter or number, to inform the player of the chord to which that bar corresponds. Typically, the player holds the zither in his arms or on a table, strums the strings with a plecturum held in his right hand, and presses down on selected chord bars with a timing in sequence clearly indicated in sheet music written in terms of simple chord bar notation. Recognizable music can be produced within minutes, and a few hours of practice and study will enable the player to entertain others, and will teach him a great many musical fundamentals.

Despite its great popularity, the chord zither has heretofore been handicapped by certain mechanical and musical limitations, some of these limitations having been inherited from the classical zither design, and some of which have arisen out of the addition of chord bars, and associated mechanisms. As will be explained hereinafter, the major mechanical and musical objection to the chord zither as presently known are overcome by the novel and unique construction shown in the present invention.

The design of a zither inherently involves great mechanical stress because of string tension. Thus, in a typical first quality zither, such as illustrated in the following specification, has 37 steel strings extending for the length of the zither, and under high tension when tuned. The main body of the zither, upon which these strings are mounted, must be made very strong in order to resist the compression and bending stresses produced by so many highly tensioned strings. Unfortunately, the requirement of great structural strength to absorb the great string tension forces is in direct conflict with the musical requirement of providing a sound box cavity of maximum size within the zither body. Moreover, zithers are made of wood, because only wood construction has been found to give the best acoustically resonant qualities for music production. There has been some use of plastic materials, and the application of the present invention includes sound box construction of any suitable acoustically resonant material, even if other than wood. However, throughout this specification, the sound box is referred to as being of wood construction, since construction of a zithers sound box out of other material is almost unknown up to the present.

The tuning system used in zithers presently known is generally of the tuning pin type. Each string is anchored to a small metal or wooden pin or peg which are set vertically into holes in the upper surface of the zither sound box, along one side of the zither. These tuning pins are held only by friction, and tend to loosen because of age, or during use, or because of temperature changes, with the result that it is difiicult to keep the zither in tune.

Another objection to the tuning pins presenly used on zithers is that they clutter the top surface of the zither. They interfere with the players strumming hand in some positions of playing. Also, the zither sound box must be constructed with a massive block of wood along the tuning pin side of the zither, so as to provide a sound base for those tuning pins. The tuning pin block thus required contributes very little to the zithers resistance to string tension, and has the serious disadvantage that it further reduces the size of the sound box cavity.

In summary, zithers presently known are notoriously prone to get out of tune because of temperature or humidity changes, or merely some slight yielding of the sound box structure under the great force of the string tension; and furthermore, the small size of sound box cavity in zithers heretofore known causes the tone of the instrument to be thin, weak in the base notes, and unsatisfactory for playing to larger groups or in larger rooms.

All presently knownchord bar mechanisms used in chord zithers have also been characterized by certain defects and limitations, both mechanical and acoustical.

From the mechanical standpoint, the outstanding defect or" presently known chord zithers is that the chord bars frequently depart from alignment, so that they do not produce the desired chord when operated. It is a universal experience of musical instrument retailers that a chord zither which has been carefully made at the factory, carefully inspected at the factory, and inspected when received by the retailer, will nevertheless be found out of adjustment after a few months in storage, or within a short time after being sold to the customer. In spite of care by both manufacturer and retailer, presently known designs lack the structural rigidity, and the reliable positive operation to assure that the chord bar mechanism, once inspected at the factory, will operate reliably for years. Although the reasons why these difiiculties are encountered with presently known zithers are not all clearly understood, certainly one major cause of recurring maladjustment has been the tendency of the chord bar structure to experience slight internal movements, and also for a tendency for the strings to vary in elevation slightly, because of the lack of precision of tuning pins. In some cases, one or more strings are moving slightly upward toward the chord bar, or slightly downward away from it; the player finds that he must press very hard on one chord bar, but only very softly on another; moreover, he will find amazing differences in variations from one instrument to another, having the same model number and coming from the same manufacturer.

From a music, or acoustic, standpoint, the outstanding objection to presently known chord bar zithers is their limitation to approximately fifteen chord bars. Different types of popular music, and different types of classical music, require different sets of chords. In the past, chord bar zither manufacturers have simply manufactured different zithers for each type of music. No attempt has been made to provide a zither in which the chord mechanism could be shifted from one chord arrangement to another.

The foregoing are but a few of the most important objections to the chord zithers known up to the present time. The invention described herein overcomes all of these objections, when all the novel features disclosed are combined in the preferred form of the invention. However, in its simplest and most generic form, the chord zither of the present invention provides a zither which rarely has to be retuned, and which produces much richer and deeper tone than zithers known in the past. The present zither employs a sound box of much lighter construction than the massive plank-like structures used in even small zithers of the past. The sound box is framed in a very strong but light frame, such as a frame of tubular steel, upon which the strings are mounted, and tuned, and which retains the strings at unchanging tension, regardless of ordinary changes in temperature and humidity, and regardless of moderate changes in the sound box structure. The chord bar mechanism of the present invention relies upon the surrounding frame of tubular metal (or some equivalent structure) to achieve a rigidity which keeps the chord bars in precise adjustment. Heretofore, it was believed that the chord bar mechanism required the same massive sound box structure as was required for the string tension. In the present invention, however, greater rigidity is achieved despite the mounting of the chord bar mechanism on a lighter sound box, since the points of mounting of the chord bar mechanism are located close enough to the tubular metal frame so that they are held in unchanging alignment.

In a preferred form of the present invention, the chord bars are housed in a magazine which may be shifted to any one of several positions above the strings, so that one set of fifteen chord bars, shiftable to twelve positions, may provide as many as one hundred and eighty different chords, instead of the fifteen usually found in a chord zither. Also, different chord bar magazines are readily interchangeable. In a simplified form of the invention, magazines of different chord bars may be simply interchanged, without provision for shifting within the bridge structure housing.

Interchangeability and shiftability of the magazine containing the chord bars, makes it impossible to rely upon the various kinds of chord bar operating buttons heretofore known. These have generally been mounted directly to the chord bar. In the forms of the present invention which involved the use of a magazine, however, it is preferred to employ operating buttons which are movably mounted in the bridge structure, with the chord bars and their magazine freely slidable under said push buttons, or removable from them.

The foregoing and many other objects and advantages of the present invention will be understood from the following description of a preferred form of the novel chord zither. This preferred form incorporates many refinements, and it is to be understood that the invention is not restricted to a design incorporating all those refinements,

4 but is intended to include all modifications and simplifications which incorporate the basic novel features of relatively light sound box, enclosed within a strong and rigid outer frame, and supporting chord bars in a bridge structure which is anchored directly or indirectly to the surrounding frame. The description should be read in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of a chord zither constructed according to the invention;

FIG. 2 is a plane view of the chord zither illustrated in FIG. 1;

FIG. 3 is a longitudinal sectional view taken at a vertical plane indicated in FIG. 2. by the arrows 3-3, as viewed in the direction of those arrows; the section view of FIG. 3 is substantially enlarged to show details, but a large middle section has been removed as indicated, in order to reduce the length of the illustration;

FIG. 4 is a transverse section view, taken at a vertical plane, and viewed in the direction of the arrows indicated by the numerals 4-4 in FIG. 2;

FIGS. 5a and 5b are perspective views of the bridge structure sidewalls and the chord bar magazines, respectively, with their center sections removed for purposes of compact illustration;

FIG. 6 is a fragmentary sectional detail view, looking down at a horizontal plane indicated in FIG. 4 by the numerals 66, and showing the indexing mechanism for positioning the chord bar magazine at each of the several positions to which it may be shifted;

FIG. 3a is a corner detail of the chord zither, seen in perspective, in the direction of the arrow 3a in FIG. 2, showing the preferred form of micrometer screwed turning;

FIG. 7a is a perspective view of a chord bar, illustrated with a chord bar operating button positioned on it;

FIG. 7b is a detail of a fragmentary corner of the chord bar magazine, seen in perspective, showing the vertical slots in which the ends of the chord bars are seated on helical springs, to provide a resilient mounting;

FIG. 8 is a plan view of the preferred form of wooden structure for the interior of the sound box of the chord zither of the invention, shown with the upper and lower panels removed, to reveal internal construction, but with the sound hole location indicated in dashed outline; and

FIGS. 9 and 10 are two longitudinal sectional views of the sound box construction of FIG. 8, seen at the vertical planes indicated by the arrows 99 and 10-10, respectively, in FIG. 8.

A preferred form of the chord zither of the invention is illustrated in FIGS. 1 and 2, in perspective and plan views, respectively, and is designated generally by the numeral 10.

The major parts of the chord zither 10 are a shallow wooden sound box 11, approximately a right triangle in plan view; a triangular outer frame 12, preferably made of chrome plated steel tubing; a bridge structure :13, preferably constructed with wooden sidewalls and an aluminum plate prop, as will be described hereinafter; and a chord bar magazine, which is transversely slidable within the bridge structure 13.

The chord bar magazine 14 contains sixteen chord bars (one of which is actually a damper bar), these bars being identified generally by the numeral 15 as seen, for example, in cross-section in FIG. 3.

The top part of the bridge structure 13 serves as a key table '16, which is a rectangular aluminum plate about A; of an inch thick in the embodiment illustrated. Mounted in key table 16 are sixteen depressible keys, indicated generally by the numeral 17. The keys 17 oper ate the chord bars 15 as will be described hereinafter.

The strings of the chord zither -10 are designated generally by the numeral 18, and are tuned at the left end of the zither 10 (as viewed in FIG. 2) by means of a micrometer screw tuning system indicated generally by the numeral 19.

The strings 18, in the illustrated chord zither and in many other chord zithers, are 37 in number. They are tuned chromatically (i.e. at half-tone intervals) which provide three full octaves on the instrument. The range extends from F below middle C to the F two octaves above middle C.

The set of chord bars contains fifteen bars with spaced pieces of felt and openings on the undersides, as may be seen in FIG. 7a, all constructed as well known in presently existing chord zithers. However, a sixteenth chord bar is provided with felt along its entire underside, to serve as a damper bar.

The shape of the preferred form of chord zither 10 is triangular, and particularly a right triangle. Some previous zithers have also been triangular, but most of them have had a trapezoidal form, because heavy wooden plank-like parts were required to absorb string tension. In the present invention, substantially all the tension in the strings 18 is transmitted to the triangular tubular steel frame 12. Consequently, the frame shape 12 is dictated only by the requirements of the length of strings 18. In the design illustrated, the strings 18 are anchored to the hypotenuse side 21 of the frame '12. At their opposite ends, where they are anchored by tuning system 19, the strings 18 pass over a transverse side member 22 of the frame 12. A longitudinal side member 23, parallel to the strings 18, completes the triangle of frame 12.

In describing the chord zither 10, the three dimensions of the zither will be referred to as the string-axis dimension, parallel with side member 23, the transverse dimension, transverse to the strings 18 and parallel with side member 22; and the remaining dimension is conveniently designated and identified as sidewall height, being the vertical dimension of the zither sound box 11, best seen in the sectional views of FIGS. 3 and 4, in which the sound box vertical side walls are seen sectionally at 31, 32, 33 and 34.

The sectional views of FIGS. 3 and 4 may be compared With the plan view of the sound box frame 30, with all other parts removed, seen in FIG. 8, and also the sectional views of the frame 30, seen in FIGS. 9 and 10. The principal parts of the sound box frame are seen to be a relatively massive head block 31, and a smaller but also relatively massive foot block 32; and relatively thin long side walls 33 and 34.

The sound box frame 30 is covered by an upper panel 35 and a lower panel 36, both being thin resilient panels of wood with acoustic properties suitable for musical instruments. Panels 35 and 36 correspond to the similar panels in a violin or other string instrument, and vibrate to some degree along with the air contained within sound box cavity 37. Excessive vibration or movement of the panels 35 and 36 is prevented by internal bracing 38 (seen in plan in FIG. 8), vertical support being particularly required in the vicinity of the sound hole 39; for example, see the vertical column 38a in FIG. 3 and FIG. 8, which supports one side of sound hole 39, the hole location being indicated in FIG. 8 by the phantom outline.

The sound box frame 30 is closely received within the tubular steel outer frame 12. Also, the sound box 11 is provided with great rigidity and strength by being anchored to the frame 12. In the particular chord zither illustrated in FIGS. 1 to 4, two methods of anchoring are provided, although in a particular construction, either one alone would suffice. One form of anchoring is by screws inserted from the interior of sound box frame 30, passing completely through the frame and through drill holes in the inner surface of the outer frame 12. A set of such anchoring screws is illustrated in the cross-sectional views of FIGS. 3 and 4. Screw 40 passes through foot block 32 and drill hole 40a; screws 41 and 42 pass 6 through side walls 33 and 34 and drill holes 33a and 34a respectively.

However, the second method of anchoring is much preferred, and has been found adequate for anchoring outer frame 12 and sound box :11 in permanent assembly with each other, Without the additional use of screws such as screws 40, 41 and 42. This preferred method of anchoring is simply to attach the outer frame 12 is assembled position by means of bridges of a suitable plastic resin. A preferred material for this purpose is one of the epoxy plastics, such as are used in the construction of boats. The epoxy resin is prepared by mixing it with a hardening catalyst; for a few minutes it may be tamped into place and trimmed to a smooth surface; after that it will harden into a very strong ridge of material bonded to both the wood of the sound box and the steel surfaces of the outer frame 12. In the chord zither 10, it may be seen from the cross-sectional FIGS. 3 and 4 that the plastic material, as shown at 45, 46, 47 and 48 forms a pair of continuous bonding ridges one just above and one just below a horizontal plane indicated by the numeral 49 in FIG. 3, which is defined by the peripheral line of contact between sound box frame 30 and outer frame 12.

In the preferred form illustrated, upper panel 35 projects horizontally about a quarter of an inch all the way around the periphery of sound box frame 30, making substantially tangential contact with the top of the tubular metal outer frame 12.

Sound box frame 12 may be provided with an outer frame support step 50, seen in plan in FIG. 8, and in section in FIG. 3. In the particular construction illustrated, step 50 is a lower projecting shoulder portion of the head block 31, and supports only the transverse member 22 of outer frame 12. However, it will be obvious that the step could be extended around the lower periphery of sound box frame 12 if further support for outer frame 12 is found desirable for a particular construction.

The strings 18 are mounted on the chord zither 10 in a unique fashion best illustrated in FIGS. 3 and 3a. Strings 18 are supported a fraction of an inch above upper panel 35 by means of fret ridges 51 and 52, which may be seen in plan view in FIG. 2. Strings 18 are preferably made of a high grade steel piano wire, suitable weighted for the lower note strings. Consequently, although fret ridges 51 and 52 may be wood or plastic, it is desirable to protect their edges by means of transverse steel rods 51a and 52a.

As seen in the plan view of FIG. 2, and the cross-sectional view of FIG. 3, each of the strings 18 has its foot end anchored to tubular frame 12. For example, in the chord zither 10, the foot end of each string 18 passes through diametrically opposite bore holes 55 anl 56 in the outer frame 12, and is tied to a small tie-bar 57.

The tuning system 19 of chord zither 10 anchors the head end of the strings .18. In the cross-sectional view of FIG. 3, and the detail perspective view of FIG. 3a, it is seen that the tuning system 19 is comprised of a series of tuning screws 61, associated tuning nuts 62, and an anchor plate 63. In the plan view of FIG. 2, the edge of anchor plate 63 can be seen and also the outer edges of the 37 screws 61 and nut 62, a screw and nut set being provided for each of the 37 strings.

The cross-sectional view of FIG. 3 reveals that anchor plate 63 is screwed by screws 64 to a recess 65 provided in foot block 31.

FIGS. 3 and 3a also show, as a preferred form of the invention, that the strings 18 are laid over the upper and outer quadrant of the transverse member 22 of outer frame 12, so that each string is tuned by a vertical pull exerted by tuning screw 61. As tuning screw 61 is turned, for tightening, for example, the tuning nut 62 is pulled down, and a string 18 attached to the nut by an anchoring knot 66 is tightened. The downwardly moving nut 62 slides over the outer surface of the step 50 of head block 31.

It will be seen that substantially all of the tension of strings 18 is absorbed by outer frame 12. Some compressive forces are transmitted through fret ridges 51 and 52 and tuning plate 65 to the sound box frame 30, but these do not require the massive construction found in the sound boxes of zithers heretofore known. Thus, the sound cavity 37, as illustrated in FIGS. 3 and 4, is many times larger than the sound cavities found in chord zithers and classical zithers of the past.

It will also be seen that the use of the outer frame 12 for mounting the strings 18 has entirely eliminated the notoriously bad tuning problem of zithers. Whereas zithers of the past have tended to go out of tune overnight, the chord zither 10 has been found to stay in tune almost indefinitely, unless there are extreme swings in the temperature.

A typical chord bar 15, as used in the present invention, is illustrated in perspective in FIG. 7a. Chord bar 15 resembles the chord bars of prior art, with this important difference: the key 17, used to operate the chord bar 15, is not attached to the chord bar, in the preferred form of the invention. Instead, key 17 has an underside slot 70, into which chord bar 15 is slidably received. The upper part of key 17 is a button 71 which projects upwardly through key openings 72 (see cross-sectional views FIG. 3 and FIG. 4) in key table 16.

The chord bar 15 is constructed of a bar member 75 and a series of spaced felt pads 76. Bar member 75 may be wood, pressed composition wood, plastic, or the like. Felt pads 76 are arranged to dampen certain strings, but with spaces allowing others to vibrate, in a different arrangement for each chord bar, to produce the chords desired. In the present invention, the chord bar 15 must have its felt pads 76 specially designed, different from the chord bars of the prior art, so that the chord bar may produce different chords when shifted longitudinally of the chord bar (transversely over the strings 18).

In the preferred form of the present invention, the chord bars 15 are permanently housed in the chord bar magazine 14, which may be seen in the perspective view of FIG. B. The magazine 14 is substantially an inverted sheet metal box structure bridging the strings 18, and is seen to be comprised principally of the chord bar housing 80, and right and left pedestals 81 and 82, respectively. Right pedestal 81 is seen in cross-section on the left side of FIG. 4 (because of the direction of viewing) and left pedestal 82 is seen on the right side of FIG. 4.

The cross-sectional views of FIGS. 3 and 4 reveal that the chord bar housing portion 18 is entirely open underneath, as indicated at 83, to permit the downward movement into contact with the strings 18 of any of the chord bars 15. Also, the upper wall 84 of the chord bar housing 18 has a large rectangular opening 85, exposing the upper edges of the chord bars 15 to contact with the corresponding keys 17, as illustrated in FIG. 7A.

Each of the sixteen chord bars 15 (15 true chord bars and one damper bar) is resiliently supported over the strings 18 by a pair of small coil springs, 88 and 89 as viewed in the cross-sectional view in FIG. 4. The fragmentary detail view of FIG. 7B reveals the internal construction of left pedestal 82, right pedestal 81 being constructed in exactly the same manner, except facing opposite. The interior space of pedestal 82 serves as a chamber 90 for housing the springs 89, chamber 90 being compartmented by vertical partition 91 into individual compartments 92 for each of the springs 89. The fragmentary perspective view of FIG. 7B and the transverse cross-sectional view of FIG. 4 reveal that each end of the bar member 75 of the chord bars 15 is vertically movable within the upper part of one of the spring compartments 92, being supported at right and left ends by springs 88 and 89, respectively.

The chord bar magazine 14 is housed in the bridge structure 13, which is preferably constructed as illustrated of a key table 100 supported on sidewalls 101 and 102,

which latter are seen in perspective in FIG. 5A. A desirable form of construction is to use a light but very strong aluminum plate for key table 100, and a good quality of hardwood for sidewalls 101 and 102. The bridge structure 13, when assembled, is anchored to sound box 11 by means of screws 103. It is important, in order to achieve substantial rigidity at construction, that the anchoring screws 103 be received into the sound box 11 at points very near to outer frame 12.

In the preferred form of the invention illustrated, magazine 14 is transversely slidable, on its pedestals 81 and 82, within the bridge structure 13, in order by its position, to provide the player with a wide range of choices in chord bar operation. To provide for positive location of the chord bar magazine 14 in any of its several positions, an indexing mechanism 110, is illustrated in FIG. 6. This indexing mechanism is comprised of a spring detent ball 111, resiliently mounted in a recess 112 in the sidewall 101. The ball 111 snaps into position in any one of several indexing holes 113 in the side of chord bar housing 80.

It will be noted in this connection, that the upper opening in the chord bar housing 80 has sufficient length, in the direction of chord bars 15, to permit operative contact between the keys 17 and the chord bar 15 for all the transverse positions of the magazine 14 within the bridge structure 13. Although the cross-sectional view of FIG. 4, and th horizontal sectional view of FIG. 6 show only six indexing holes 113, because of difficulty in illustrating a larger number, the usual number of index positions, in corresponding holes 113, is twelve. Thus, with fifteen chord bars, and twelve indexing positions, 180 different chords may be played in a typical embodiment of the zither 10, as illustrated.

As seen in the'preferred construction, in FIG. 2, a larger key 17A is used over the chord bar 15A (see the longitudinal sectional view of FIG. 3) which serves as a damper for all of the strings 18.

Also, the upper surface of key table is provided with identifying labels adjacent each of the key openings 72 adjacent the upper ends 71 of each of the keys 17.

As seen in FIG. SE, a chord identifying card 211 is attached to the upper surface of magazine 14. One line of card 211 can be read by the player through a window 212 provided in the key table 100. In this way, the player knows in which index position he has placed chord bar magazine 14 within the bridge structure 13.

An additional convenient teaching aid is a chord bar description card 113 which is attached to the upper surface of key table 100, and has printed on it some explanatory material for each of the chord bars 15.

It will be seen from the foregoing, that the present invention, in its preferred form, provides for transversely sliding magazine 14 within bridge structure 13. It will be obvious that several different magazines 14 might be employed, each having a distinctive set of chord bars 15. Also, it will be obvious that the invention could be simplified by eliminating the transverse sliding feature, while retaining chord bar magazine 14 independent of the bridge structure 13. Thus, one could switch chord bars by substituting magazines 14, even without the transverse sliding feature of the preferred embodiment illustrated.

Many other variations, modifications, simplifications, and changes in the invention might be made, Without departing from the scope of the invention in its broadest and most general sense. It is my intention to comprehend all such modifications within the boundaries of the following claims.

I claim:

1. A chord zither which includes:

an elongated, shallow sound box, made of acoustically resonant material and having a relatively long string-axis dimension extending from a head end to foot end, a shorter transverse dimension, and a substantially smaller sidewall height normal to said string-axis and transverse dimensions;

an outer frame of material substantially stronger and more rigid than said sound-box material, said outer frame closely enclosing said sound box;

a set of strings corresponding to a predetermined series of musical notes disposed above said sound box and extending in said string-axis dimension, said strings being anchored to said outer frame at their ends toward said foot end and passing over said outer frame at said head end;

a tuning system comprised of a set of adjustable anchors,

one for each of said strings, said anchors being attached to said zither at said head end to carry the tension of said strings between head and foot ends of said outer frame;

a bridge structure disposed over said strings and based at each end near said outer frame; and

a set of chord bars contained within said bridge structure, each of said bars being individually manually movable into contact with said strings.

2. A chord zither as described in claim 1 in which:

said sound box is constructed with relatively massive head and foot blocks at each end of said string-axis dimensions, sidewalls of substantially lighter construction than said blocks, said sidewalls connecting corresponding ends of said head and foot blocks to form a sound box frame, an upper panel with fret ridges supporting said strings and having a sound hole, a lower panel closing the opposite side of said sound box frame, said panels being substantially less stiff than said side walls, and internal bracing means for supporting of said panels; and said bridge structure is mounted on said head block with attachment points near said outer frame.

3. A chord zither as described in claim 2, in which:

said head block is provided with an outwardly projecting step under the head end of said outer frame, and each of said adjustable anchor-s comprises a vertically disposed screw anchored to said step below said outer frame, and an anchor nut vertically movable on the outer surface of said step, by rotation of said screw, thereby applying tuning tension to a zither string attached to said anchor nut.

4. A chord zither as described in claim 1, in which:

said chord bars are housed in a magazine, which is slidable within said bridge structure transversely over said strings, and said bridge structure has walls at at least one side of said zither defining an opening to permit the removal of said magazine with its contained set of chord bars, and the substitution of another magazine containing a different set of chord bars.

5. A chord zither as described in claim 4, in which:

a set of buttons for individual opration of each of said chord bars is permanently retained in the top portion of said bridge structure, said buttons being vertically movable in said bridge structure to depress a corresponding chord bar contained within said magazine within said bridge structure, and said buttons having under surfaces permitting the transverse sliding movement of said magazine to different positions of said magazine over said strings, and to permit the removal of said magazine from said bridge structure.

6. A chord zither which includes:

a sound box constructed of a material equal in musical properties to the wood of stringed wooden instruments, said sound box having a relatively long string axis dimension, a shorter transverse dimension, and a substantially smaller sidewall height normal to said string-axis and transverse dimensions, said sound box being constructed with relatively massive head and foot blocks at each end of said string-axis dimension, sidewalls of substantially lighter construction than said blocks, said sidewalls connecting corresponding ends of said head and foot blocks to form a sound box frame, an upper panel with fret ridges and a sound hole, a lower panel closing the opposite side of said sound box frame, said panels being substantially less stiff than said side walls, and internal bracing means for support of said panels;

an outer frame, said outer frame comprising a closed peripheral structure of rigid metal tubing closely enclosing said sound box and including anchoring means anchoring said outer frame to said sound box;

a set of strings corresponding to a predetermined series of musical notes disposed above said upper panel on said fret ridges and extending in said string-axis dimension each of said strings being anchored to said outer frame at its end, and having its head block end wrapped over the surface of said outer frame;

a tuning system comprised of an anchoring plate at said head block end, a set of screw adjustable anchors, one for each of said strings, individually anchoring the head block ends of said strings to said anchoring plate;

a bridge structure disposed over said strings transversely thereof and supported on said head block adjacent said tubular frame;

a chord bar magazine transversely movable over said strings within said bridge structure; and

a set of chord bars disposed transversely of said strings within said magazine, and resilient support means for each support bar, each of said chord bars being downwardly movable in said magazine against said resilient support means, for selective manual application to said strings.

7. A chord zither as described in claim 6, which includes an index stop mechanism in said bridge structure, and

contacting said chord bar magazine, to provide positive location of said chord bar magazine at a plurality of positions transversely of said strings, for providing different chord bar musical arrangements for each of said chord bar magazine positions;

a table of musical information displayed on the top side of said chord bar magazine, one set of information for each of siad indexed magazine positions; and

an information viewing window in the top of said bridge structure for presenting to the view of the player, for each indexable position of said chord bar magazine, the particular musical information relevant to said position.

8. A chord zither as described in claim 6, which includes:

a top wall in said chord bar magazine which is provided with an opening exposing the top sides of said chord bars over a substantial part of their length;

a set of chord bar operating keys, one for each of said chord bars, mounted in the top of said bridge structure, and vertically movable therein, each of said keys being provided with a pair of downwardly depending flanges closely received on opposite sides of a corresponding chord bar, to permit said chord bars to be shifted transversely of said strings, and to permit operation of said chord bars for all said transverse positions of said chord bar, by said keys.

9. A chord zither as described in claim 6-, in which:

said outer frame is positively located on, and anchored to the outer side walls of said sound box frame by laterally projecting wall structure above and below said outer frame, closely receiving said outer frame and adhesively attached to it.

10. A chord zither as described in claim 6, in which:

said chord bar magazine includes right and left pedestals, disposed in parallel with the string axis dimension of said zither, at each side of zither, and supporting the remaining structure of said magazine above said set of strings, the bottoms of said right and left pedestals being adapted to move slidably over the upper surface of said upper panel;

each of said pedestals includes internal wall structure defining a set of vertical slots, one for each of said chord bars, the opposite slots in said right and left pedestals confining and guiding the corresponding chord bars in precise vertical movement; and in which a resilient coil spring is provided in each of said slots below each end of each of said chord bars for resiliently urging the corresponding chord bar upwardly, within said magazine, to a. position retracted from contact with said set of strings.

References Cited UNITED STATES PATENTS 12/1896 Dolge 5/ 1901 Stewart 2/ 1920 Cohn 4/ 1926 Hanson US. Cl. X.R.

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