US2657610A

US2657610A - Tabular device for musical modulation

Info

Publication number: US2657610A
Application number: US155531A
Authority: US
Inventors: Jr Walter E Carran
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-04-12
Filing date: 1950-04-12
Publication date: 1953-11-03
Anticipated expiration: 1970-11-03

Description

NOV- 3 1953 w. E. CARRAN, JR 2,657,610

TABULAR DEVICE FOR MUSICAL MODULATION Filed April l2, 1950 3 Sheets-Sheet l Nov. 3, 1953 w. E. CARRAN, JR 2,657,610

TABULAR DEVICE FOR MUSICAL MODULATION Filed April 12, 1950 3 Sheets-Shea?. 2

COMMON j K E Y NOVu 3, 1953 WI E CARRAN, JR 2,657,610

TABULR DEVICE FOR MUSICAL MQDULATION Filed .April l2, 1950 3 Sheets-Sheet 5 (IHOHO (IMOHO N 4T fm1/enfer Waer Car/'ava J2' k Patented Nov. 3, 1953 UNITED STATES FFlCE TABULAR DEVICE FOR MUSICAL MODULATION 7 Claims.

This invention relates to a device for use in musical composition or arrangement to deter mine the chords by which the musician may modulate a musical composition from one kcj to another. Modulation, or the transition from one given key to another without a break in the chord succession, may be accomplished by nding a chord, usually a triad, common to both keys or, when there is no common chord, by selecting a third key in which there are two or more chords one common to the iirst and third keys and another common to the second and third keys. Either a common chord, if any, or a common key may act as a modulation link between the two given keys.

One object of the present invention is to pro vide a mechanical device with which a musician or a student may quickly determine the inodulation link or links between two given keys. A further object is to provide a device which compact and simple to operate, and economical to manufacture.

In one aspect the invention involves a slide rule of the straight or rotary type comprising a base marked with the notes of a musical scale, usually the chromatic scale, a slide or rotor adjustable relative to the base and having a mark for indicating on the base a distinctive note such as the tonic note of one of two given keys, the slide carrying a series of indicia,

for instance numerals, each representing one of the chords in a key, preferably the triads, and arranged inV diierent positions so as to indicate distinctively the classification of the chords designated, and a cursor also adjustable relative to the base, the cursor having means such as a window for indicating on the base a distinctive note, for example the tonic note, of the other of said two given keys, and indicators which may be other windows for selecting indicia on the slide which represent chords common to said given keys. Adjustment of the slide may be linear or rotary, accordingly as the slides are of the straight or rotary type. More specifically the indicia on the slide are spaced lengthwise of the slide at the same intervals as the notes in any of the diatonic scales included in the chro matic scale on the base and are distributed in groups extending croswise of the slide such that all indicia of a group represent chords of the same classification, i. e., one of the classifications major, minor, diminished or augmented. Lengthwise and crosswise would in the case of a rotary or curvilinear slide rule be understood respectively as parallel to and transversely of the direction of adjustment of the slide. rIhe indicators or indicia selecting windows on the cursor are arranged in the same relation as the corresponding indicia preferably so that when the mark on the slide and the aforesaid means on the cursor indicate the same note on the base, then each of the indicators will select one oi the indicia. The cursor may also carry designators or windows in addition to the aforesaid means or indicators. said designators serving to select notes on the base which are the roots of the chords in the key whose tonic note is indicated by said means. If desired a symbol defining the degree of the chord selected by a designator may be associated with each of said designators.

For determining a linking key which contains chords respectively common to one or the other oi two given keys the slide rule comprises two slides each carrying a mark for designating on the base the tonic note of the respective keys and a series of indicia disposed as aforesaid, and a cursor having means for indicating on the base an identifying note, such as the tonic or the dominant note, of a linking key and two series or indicators disposed to select indicia in each of the corresponding series which represent chords common to one of the given keys and the linking key.

From the accompanying description it will be apparent that various novel and useful subcombinations are encompassed by the invention according to the aspects described above.

For the purpose of illustration a typical embodiment of the invention is shown in the accompanying drawings in which:

Fig. 1 is a plan View of a slide rule;

Fig. 2 is a section on lines 2-2 of Fig. l; and

Figs. 3 to 6 inclusive are plan views.

in the particular embodiment of the invention chosen for the purpose of illustration the slide rule comprises a base Zi having the notes of the chromatic scale 22 marked at regular intervals lengthwise at the middle of the base, a pair of slides 23 and iii tted in tracks above and below the scale and a cursor I3 slidingly tted on the base over the slides. As shown in Figs. 4 and 6 each of the slides 23 and lli are marked with two series l? and llc oi the numerals l to 7 repeated twice. Each of the numerals or indicia denotes a chord whose root is one of the seven degrees of a major or minor key, and, of course, also represents the root itself. Preferably the series li' and lla of numerals are of distinctive colors. Lengthwise of the slide the numbers in a series are spaced at the same intervals as the notes of any of the diatonic scales included in the chromatic scale on the base. For example, the diatonic scale in the key of B nat major comprises the notes B flat, C, D, E flat, F, G, and A. These notes are the roots of the seven triads in the key of B flat major which may be represented by the Arabic numerals 1 to 7. With reference to Figs. 4 to 6 it can be seen that on the slides 23 or Il the numerals opposite the words major key chord are vertically aligned with the notes on the base which are the roots of the chords. Thus the Arabic numeral 1 and the Arabic numeral 2 representing the triads of the first and' second degree are spaced apart the same hori-A zontal interval as the notes B iiat` and Q likef.

wise the

numerals

3 and 4 are spaced the sameY as the notes D and E nat which are the rotsI of the chords represented by the numerals, It, will be noted that the numerals on slides 23 or I4 opposite the words minor key chord are spaced at different intervals than the numerals representing the major key chords. For example, the numerals 2 and 3v in the minor key series are in adjacent spaces whereas the numerals 2v and 3 in the major key series are onev space apart for the reason that the chords of the third de.- gree in any parallel major and minor keys do not have the same root. For example in the key of B- flat major the root of the third triad is D4 whereas the root of the third chord in B iiat minor is D flat as may be Verified by the verticall alignment of the corresponding numerals and letters in Figs. 4 to 6-.

In addition to being arrangedinl the above described horizontal order lengthwise ci the slides 23 and I4, the numerals I1'Ii andl Hc are disposed in vertical groups according to the intervals between the three notes of the triad represented by each numeral. triads in a major key are customarily classied as major, minor or diminished chords, the first, fourth and f-th degree triads being major, the second, third and sixth triads being minor and the seventh triad being a diminished chord. In a minor key the fth and sixth triads are olassified as major chords, the first and fourth minor, the second and seventh diminished and the thirdis an augmented triad. rl'hus the numerals. ilV representing the triads of any major key are distributed in three groups disposed crosswise of the slides 23- and I4 and the numerals Ila representing the seven triads or the minor key are distributed in four groups, so that each numeral by its position in the horizontal order and in th-e vertical grouping distinctly represents a specic chord. The arrangement ofl the numeralson` the lower slide I4 is the same as that on the upper slide 23 except that the major and minor key series are inverted.

The numeral l at the beginning or end ofthe major or minor series on either slide is distinguished from the other numerals by the heavy vertical lines I5 and is used as a marker for indicating the note on the base which is the tonic note of a particular or given key. For instance in Fig. 1 the slide 23 is set so that the numeral 1 in both the major and minor series indicates the note B which is the tonic note of: the keys or B major and minor. The other numerals in the major and minor series are then disposed in vertical alignment with the notes on the base which are roots of the chords which said other numerals represent. Thus the root of the triad or'k the second degree in the key of B major or minor is C sharp, the root of the triad ofthe third degree For example the in B major is D sharp while the root of the chord of the third degree in B minor is D. f

The cursor I6 which appears in Figs. l and 3 superimposed over the slides 23 and I4 and the base scale 22 is divided into right and left halves each of which has four series of windows or indicators corresponding to the four series of nu merals oni the slides 23 and I4. Each half of the cursor also has a fifth series of central` windows or designators corresponding to the notes 22 on the base 2|. The series of windows I8 and Il and the series Illa and Ila correspond to a series of, numerals Il and Ila respectively on slides 2S and I4. The central windows comprise a first set including Window 8 and six windows 8a, and a second set including the Window 9 and the six windows4 3a, For simplicity in construction two adjacent windows, such as 9 and Ga to the left offtlieA words common minor key, are shown. as one double window, but might be framed individually and will be considered as two separate Windows.

The windows B and 8a are spaced lengthwise of the cursor at the same intervals as the windows Inf andl lua, namely at the same intervals as the diatonic scale of a major key on the.v base. The windows 9. and 9a are spaced at the same intervals as the windows II and IIza, namely at the intervals of the diatonic scale in a minor key. The windows 8a will expose the remaining six notes of the major key of which the tonic note; exposed by window 8. Similarly when window 9i exposes the tonic note of a minor key the windows 9a expose the remaining notes in the minor key. It should be remembered that these: notes are also the roots of the seven triads. in a key. The series of Roman numerals I2 and I3 are located vertically above or below the windows 8 and 8a. and 9 and 9a respectively to symbolize the degree of chord of which the exposed note is the root.

The operation of the slide rule is illustrated in Figs. l and 3.

CHORDS COMMON TO rFWO GIVEN KEYS Example I To4 find the. chords common to two major keys two. general methods are available.

(a). The determination of chords common to. the keys of B and E- major is shown in Fig. 1. The` upper scale 23 is adjusted so that the numeral l betweenl the heavy vertical lines l5f is set above. the` note B on the base 22. The lower slide I4 is adjusted so that the numeral 1 is below the note E. The cursor is then adjusted so that the Window B. for exposing the tonic note of a key exposes the note B.. Since thenumeral 1 of the upper slide indicates, and the window B of the cursor selects the same tonic note, the windows Il) will expose numerals of the` major series I'I representing the chords whose roots are exposed by the windows 8. and 8a. The lower set of windows I0 expose numerals II- onv the lower slide I4 which represent chords in the key of E. which are also present in the key of B major. By comparing each numeral appearing. in a window I0- on the upper half of the cursor with the numerals appearing in the Window ID vertical-ly aligned therewith and on the` lower half of the cursor it can be seen that the triads of the first, second, fourth andrsixth degree in thekey of B, major are the same as the fifth, sixth, first and third triads respectively of the key of E major. The notes combining to form any one of these triads may be` drivedA from the notes appearingv through windows 8 and Sa by combining the root note of the chord shown in one of the Windows 8 or `8a with the third and fifth notes above the root note. For example the rst triad of l2 which is the fifth triad of E major compris notes B, D sharp and F sharp.

(b) The chords common to two major keys may also be found by adjusting the upper slide 23 so that the numeral 1 indicates the tonic note of one of the keys, and by exposing the tonic note of the other key through the window 8. For example, in Fig. 3 numeral 1 on slide 23 indicates the key of B major and the window on the cursor I6 indicates the tonic note of the key of E major. Now if the numerals Il which appear through the windows I0 and which represent the triads of B major are compared with the Roman numerals l2 disposed vertically above the Windows 8 and 8a. and representing the triads of li. major, it is again seen that the first, third, fifth and sixth triads in the key of E major are identical with the fourth, sixth, rst and second triads respectively in the key of B major.

Example II Chords common to a major and a minor key may be determined as follows:

(a) The determination of the triads common to B major and E minor is illustratedinFig. 1. The

upper slide 23 is set with the numeral 1 above the note B, the lower slide lli is set with the numeral 1 opposite the note E, and the cursor is set so that the left-hand window Il exposes the tonic note B of the major key of B. Comparing the Arabic numerals lla on the lower slide I4 which appear through the windows Ica with the Roman numerals I2 appearing above the notes exposed by the Windows 8 and da it is seen that the first triad of B major is identical with the fth triad of E minor.

(b) The chords common to a major and a minor key may also be found by setting the numeral I of the upper slide 23 opposite the tonic note of the major key and setting the window 9 of the cursor to expose the tonic note of the other key and observing the Arabic numerals Il appearing through the windows I I. As shown in Fig. 3 the numeral 1 which is related to the key of B major indicated by the upper slide 23 represents a triad which is identical with the fifth triad of the key of E minor as designated by the Roman numeral V above the root note B on the base.

Example III Chords common to two minor keys may be found as follows:

(a) The determination of the chords common to the keys of B minor and E minor is illustrated in Fig. 1. As in the case of two major keys the Arabic numerals 1 of the upper slide 23 and the lower slide I4 respectively are set above and below the tonic notes of the two given keys. In this instance, however, windows Ila on the extreme upper and lower portions of the right-hand side of the cursor are compared. The cursor is set so that the tonic note of either key is exposed through the window 9. In Fig. 1 the tonic note B of the key of B minor is exposed. The windows I la on the upper half of the cursor will obviously exposed numerals representing all the triads of the key of B minor since both the cursor It and the slide 23 are set to designate or select this key. One of the windows I la on the lower half of the cursor exposes the numeral 1, representing 6 the rst triad in the key of E minor and vertically aligned with the numeral 4 in a window Ila, at the top of the cursor. Thus, the first triad in E minor is identical with the fourth triad in B minor.

(b) The chords common to two minor keys may be also determined with the use of one slide and the cursor only. With reference to Fig. 1 it can be seen that regardless of the setting of the upper slide 23 if the cursor is set so that the windows or S expose-s the note B then the windows 9 and Sa will expose the notes on the base which are the roots of the triads in B minor, these triads being identied by the Roman numerals vertically above the windows 9 and 9a. Then if the lower slide I4 is set with the numeral 1 below the note E then the windows Ila on the lower half of the cursor will expose the chord or chords in E minor which exist also in the key of B minor.

THIRD KEY HAVING CHORUS COMMON TO EITHER OF TWO GIVEN KEYS In certain cases it may happen that the two keys do not have any common chords. For example should it be desired to modulate from a composition in the key of B minor to another in the key of E` major, and in accordance with the procedure given in Example II(b), the numeral 1 of the upper slide 23 is set above the note B and the window e of the cursor set to expose the note E it will be seen by comparison of the minor key windows Illa on the upper half of the cursor that there are no chords in the key of B minor which are identical with chords in the key of E major, and it is therefore not possible to modulate from one key to another directly by a chord common to both keys. In such a case it is possible to make the transition from one given key to another through a third key, that is a passage in the first key is caused to end on a chord common to the first key and linking key. A passage of one or more additional chords is then played in the linking key, the passage ending on a chord which is common to the linking key and the second given key. Since the begin- Example IV An example of common key modulation between two keys not having common chords is illustrated in Fig. 3 with reference to the keys of B major and D major. The numeral l on the upper slide 23 is set above the note B on the base, and the numeral l on the lower slide lll is set .below the note D on the base. To determine a common major key the cursor is then progressively adjusted so that the windows Iii on the upper `and lower half of the `cursor expose various groups of numerals until numerals Il of the major key series appear in both the upper and lower series of windows IG. It is not necessary when finding a common linking key that the nu.- merals be vertically aligned as it is in determining a common chord. One setting of the cursor which satisfies this condition is shown in Fig. 3,

in which the note E identifying the key of E major appears in the window 8 beside the words Common major key, the

numerals

4, 6, 1 and 2 appearing in the upper series of windows Ill, and the

numerals

3 and 5 appearing in the lower series of window ID. This setting of the cursor indicates, for example, that the fourth triad in the key of B major is identical with the iirst triad in Ythe key of E'vmajor and `thatthesecond triad in the key of E major is identical with'the third triad in the key of D major. With this information the musician could in modulating from the'key-of B major to D vmajor play a passage of chords ending on thefourth triad 'of B major. He 'would then play fthe `third triad in the key of D major and could then continue with a passage of chords in D major having made a direct transition from B major to D major through the linking or common key'of E major. It is, of course, possible to play one or more chords in the rlinking key. The musician may play any desired number of chords so long as the first one is common to the iirst given key and the last one is common to the second given key. It is `also apparent from the illustration of Fig. 3 thatother `links are available between the key of B Ymajor and D major, for instance, from any of the fourth, sixth, rst or second triads of B major to either of the third or fth tri-ads of D major.

The above described method `of passing from one lgiven key to another through a common major 4key is applicable where it is desired to pass `from one major key to another major key, from one major key to a minor key, from a minor key to a major key or from a minor key to a second minor key by using the appropriate series of numerals and windows on the upper and lower slides 23 and I4.

Example V Where it is desired to pass from one given key, major or minor toanother given major or minor key through-a minor linking key the method of Example V is carried out using the windows on the right-hand side of the cursor IE. In the instance illustrated in Fig. 3 where it is desired Ato pass from the key or B major to the key of D major, these two keys having no common chord, through a minor key, the numeral l-on the upper slide 23 is set above the note B and the numeral l on the-lower slide I4 is set below the note D, and the cursor is adjusted while referring to numerals `appearing in the windows I l on the upper and lower half of the right-hand side -of the cursor I6, these series of windows corresponding to the major series of numerals representing chords in B major and D major. At any setting of the cursor I6 `where numerals appear in both the upper and lower series of windows II the tonic note of a linking minor key will appear in the window 9. Thus the fth triad in the 'key of E minor is identical with the rst triad in the key of B major, and the rst triad in the key of VE minor is identical with the second triad in the key of lD major. As explained above with this information it is possible to modulate from the key of B major to D major through `the linking minor key of E.

Persons particularly skilled in musical compo'- sition will be able to accomplish modulation by means of the common chord or common key without reference to the notes 22 of the scale on the base -2I `or the

corresponding windows

8, 8a, 9 and 9a along the center of the cursor I4. For

their purposes these elements of the slide rule may be omitted. For example, in modulating from the key of B major to D major through a common key the skilled musician, knowing `that there is an interval of a minor third between the two keys would merely set the two slides 23 and I4 so that there is a horizontal interval of three spaces or half tones of the chromatic scale between the numerals 1 on each of the slides. Then with reference only to the numerals inthe major or minor `series I1 or Ila appearing in windows I0 or Ia he would `be able to deter-- mine by means of the numerals alone such 'of the chords of either ofthe two given keys as are common to an existing but undetermined linking key, and would `be able to progress from one key to the other identifying the `linking chords by number or degree only without identifying their root notes on the base. Likewise in determiningr a chord common to two keys according to Example Im), Ilm) or 111m), a skilled Vmusician could identify the chords identified by the Arabic numerals ITI or Illa appearing in vertically aligned windows I0 or Ina without reference to the root notes corresponding to the numerals and appearing through

windows

8, 8a, 9 or 9a.

TRANSPOSITION With this slide rule it is also possible to transpose a composition Vfrom one key to another. The cursor I6 is removed and the numeral 1 on the upper slide 23 is set opposite-one of the keys and the numeral 1 on the lower slide I4 is set opposite the other of the keys. For each note onthe base -in the given key there will be a numeral thereabove on the slide 23 in either the series of numerals I1, in the case of a major key, or the series of numerals Ila, inthe case of a minor key. On thebase above the same numeral on the lower slide I4 is a note which `is the note in the -new vkey corresponding to the note in the given key.

Because the slide rule will quickly give all possible modulation links, whether common chords or common keys, thelarranger is aorded a variety of chord `progressions and thus may select a link appropriate to his arrangement with a minimum of lost time and effort. The present invention is also useful for instructing in the theory kci modulation as well as in arranging compositions.

It should be understood that vthe present disclosure is for the purpose of illustration only and that this inventionincludes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

l1. Amusicallslide rule for determining a modulation link between given keys, comprising a base having the notes of chromaticscale marked thereon at regular intervals, adjustable relative to the base a slide having arnark for indicating on the base adistinctive note of one of said'givenkeys, on said slide a series of modulation link indicia representing 4the chords in a key, said indicia being spaced parallel to the base at the same intervals as the notes in a diatonic scale on the base, and spaced away from the base according to the classification ofthe chord represented, also adjustable lrelative to the base a vcursor having means for indicating ron the base a distinctive note of another'of said keys and modulation link indicators disposed selectively to reveal on the slide modulation link indicia which represent chord modulation links between said given keys,

whereby the chords common to any two given keys may be determined thereby determining the modulation link between said given keys, said indicators being arranged such that when said mark and said means indicate the same note on the base each of said indicators reveals one of the modulation link indicia.

2. A musical slide rule for determining chords common to two given keys comprising a base having the notes of the chromatic scale marked thereon at regular intervals, a slide movable lengthwise of the base, said slide having a mark for indicating on the base the tonic note of one of said keys and a rst and second series of modulation link indicia symbolizing the seven chords of the major and minor modes of a key respectively, the indicia of each series being arranged in order lengthwise of the slide at the same intervals as the notes on the base in the diatonic scale of said modes, and disposed crosswise of the slide in longitudinal groups such that all the indicia of a group symbolize chords of the same classication, also movable lengthwise of the base a cursor having means for designating on the base the tonic note of the other of said given keys, and carried by the cursor a first and second series of modulation link indicators, each disposed selectively to reveal modulation link indicia symbolizing chords of said one key which are modulation links with said second key, one of said series of modulation link indicators being arranged such that when said mark and said means indicate the same note on the base, each of the indicators in said one series reveals one of the indicia of one mode, the other series of indicators being arranged like said one series, whereby common chord modulation links between keys of the same and different modes may be determined,

3. A musical slide rule for determining a modulation link between two given keys, comprising a base having the notes of a musical scale marked thereon, adjustable relative to the base first and second slides each having a mark for indicating on the base a distinctive note of one of said given keys, carried on each slide a series of modulation link indicia each representing a chord in a key and distinctively positioned relative to each other according to the classication of the chord designated, also adjustable relative to the base a cursor having two series of modulation link indicators for selectively revealing on said slides respectively modulation link indicia representing chords in said given keys which are chords in a linking key, and means on the cursor for designating on the base a note identifying said linking key, whereby chord modulation links common to said linking key and. to said given keys respectively may be determined thereby determining the chords for modulating between said given keys.

4. A musical slide rule for determining a modulation link between two given keys, comprising a base having the notes of a musical scale marked thereon, adjustable relative to the base a rst and a second slide each having a mark for indica-ting on the base a distinctive note of one of said given 'ed on each slide a series of modulation .a each representing the chords in a key, said indicia being spaced parallel to the base at the same intervals as the notes in a diatonic scale on the base, and spaced away from the base according to the classification of the chord represented, also adjustable relative to the base a cursor having means for indicating on the base a distinctive note of linking key, carried by the cursor two series of modulation link indicators for selectively revealing on said slides modulation link indicia representing roots of chords in said given keys which are roots of chords in a common key, said indicators being arranged such that when said mark and said means indicate the same root on the base, said indicators select all of said modulation link indicia, and means on the cursor for designating on the base a distinctive note of said linking key, whereby chord modulation links common to said linking key and to said given keys respectively may be determined thereby determining the chords for modulating between said given keys.

5. In a musical slide rule for determining a modulation link between two given keys, the cornbination of a base, two slides adjustable relative to the base, carried on each slide a series of modulation link indicia each representing a chord in a key and distinctively positioned crosswise of the slide according to the classication of the chord designated, and adjustable relative to the slides `a cursor having two series of modulation link indicators which reveal on said slides respectively modulation link indicia representing chords in said given keys which are chords in a linking key thereby determining the modulation links between said given keys, said cursor having a position in which each indicator of a series selects one of the modulation link indicia on one of the slides.

6. In a musical slide rule the combination of a base having the notes of a musical scale marked thereon, adjustable relative to the base two slides each having a mark for indicating on the base a distinctive note of one of two given keys, on each slide a series of modulation link indicia representing a chord in a key, the indicia of a series being spaced lengthwise of the slide at the same intervals as the notes of a diatonic scale and disposed crosswise of the slide in lengthwise groups each of which includes all indicia representing chords of the same classication, said slides being individually adjustable so that when each of said marks indicates the distinctive note of one oi said given keys, the modulation link indicia on one slide indicate on the base the root notes of the chords in said one given key, the corresponding modulation link indicia on the other slide indicating the root notes of the corersponding chords in the other key, whereby said lengthwise groups selectively determine the chords of the respective keys affording modulation links between said keys.

7. In a musical slide rule the combination of a base having the notes of the chromatic scale Imarked thereon, adjustable relative to the base two slides each having a emark for indicating on the base a distinctive note of one of two given keys, on each slide a series of modulation link indicia representing the triads in a key, the indicia of a series being spaced lengthwise of the slide at the same intervals as the notes of the diatonic scale included in the chromatic scale on the base and disposed crosswise of the slide in lengthwise groups each of which includes all indicia representing triads of the same classification, said slides being individually adjustable so that when each of said marks indicates the distinctive note of a diierent key, the modulation link indicia on one slide indicating the root notes of the triads in one given key, the corresponding indicia on the other slide indicate the root notes 11 112 of the corresponding trims in Athe other key, Number Name Daf/e whereby said iengihwise groups selectively -deter- 1367,'156 -Nix u--- July ,26, 1887 mine the chords of the respective key-s aioifding 504,57'76 Duret Sept. 12,1893 modulation links between said keys. 2,188,723 Posey Jan. 30 1940 WALTER CARRANJ'R. 5 2,502,300 Young Mar-28, 1950 .2,520,208 Green Aug. 29, :1-950 References Cited in the file of this patent UNITED .STATES PATENTS FOREIGN PATENTS Number vCountry Daz-te Number Name Date i I n :363,392 Huard May 24, 1887 10 '934 Huard --Y--- 1337 i ...i FH 1