Keyboard instrument for the natural tone system

A keyboard instrument for the natural tone system with at least one keyboard whose keys are assigned to the overtones in a predetermined sequence. According to the invention, the keyboard is optimally adapted to the conditions of the natural tone system by the fact that 16 keys are provided per octave which are arranged and constructed in such a way that the natural tones can be played in sequence on three playing levels. One peculiarity of the invention consists of the boxed arrangement of the keys on the three playing levels, whereby only the "harmonic keys" are arranged on the frontal playing level, the "melodic keys" and the tapered "harmonic keys" are arranged on the central playing level, and that the tapered section of the "melodic keys," a further tapered section of the "harmonic keys" and the "chromatic keys" are arranged on the rear playing level. The adjacent key sections on each playing level are equally wide.

BACKGROUND OF THE INVENTION 
The invention pertains to a keyboard instrument for the natural tone 
system. 
While conventional musical compositions are primarily based on the tempered 
tone system, microtonal compositions are predominately based on the 
so-called natural tone system. The term natural tone system or natural 
tone series represents the succession of overtones that are defined as an 
integral multiple of the fundamental frequency of a tone: 
EQU f(n)=f(o).times.n, with n=1, 2, 3 . . . 
In this formula n is also designated as the natural tone number. 
As compared to the overtone series, the fundamental tone in a natural tone 
series is already designated as the first natural tone. It is 
characteristic for the natural tone series or the natural tone system that 
an octave shift is always produced by a power of 2. 
It is basically possible to form arbitrary natural tone series on any 
desired fundamental frequency. To compose sensibly and perform using the 
natural tone system, it is necessary however to make a selection. This 
selection suggests that only the tones of a natural tone series defined by 
a certain fundamental frequency and their octaves are permitted as 
fundamentals. This results in natural tone series selected with reference 
to a so-called modulation factor m in accordance with the natural tone 
number as follows: 
EQU f(n,m)=f(o).times.n.times.m, with n,m=1,2,3 . . . 
The smaller the modulation factor, the larger the number of tones which the 
selected series has in common with the original natural tone series. 
The invention is based for practical reasons on the aforementioned selected 
natural tone series. However, the invention is not limited to these 
selected natural tone series. 
All types of conventional instruments, which also include keyboard 
instruments, are basically suitable for microtonal music. One problem with 
the performance of microtonally composed music on keyboard instruments can 
be seen in the fact that keyboard instruments are designed for the 
tempered tone system outlined in the subclaims. 
While the aforementioned keyboard instruments for the natural tone system 
thus far used conventional keyboards or personal computer keyboards 
designed for the tempered tone system consists of, the invention suggests 
that the number of keys per octave be increased to 16, and that their 
arrangement be designed such that the natural tones 4-7 (24), 8-15 (25,34) 
and 16-31 (26,35,40,41) are played in series on three playing levels. 
The invention thus provides a special new keyboard for the pure intervals 
contained in the natural tone scale which not only meets the requirements 
of the natural tone series, but is also compatible with the performance 
technique already learned for keyboard instruments, so that playing on the 
keyboard instrument according to the invention can also be easily learned 
by persons accustomed to conventional keyboard instruments. 
The ability to play the keyboard instrument according to the invention on 
three playing levels is attained by three different forms of keys, namely 
by "harmonic keys" that tapered twice from the front toward the rear, by 
"melodic keys" tapered only once, and by "chromatic keys" with uniform 
width. These keys are arranged relative to each other in such a way that 
only the front sections of the "harmonic keys" with a maximum width are 
located adjacent to each other in the front field or front playing level. 
In the central field or central playing level, the sections of the 
"harmonic keys" that correspond with the first tapering adjoin the front 
sections of the melodic keys with the same width, and are thus represented 
alternately with the harmonic keys in the central field. The rear field or 
rear playing level is formed by the sections of the "harmonic keys" that 
are tapered for the second time, the tapered sections of the "melodic 
keys" and the "chromatic keys" with uniform width, namely in the regular 
series: "harmonic key," "melodic key" and "chromatic key." It is 
essential that the adjacent key sections are equally wide and equally long 
or deep within each playing level. 
In other words, the structure of the keyboard of the keyboard instrument 
according to the invention provides at least three differently shaped 
types of keys in order to realize the different playing levels or key 
fields, namely a first type of key which extends over the entire depth of 
the keyboard and has a given maximum width in the frontal section, whereby 
the maximum width can, for example, correspond to the width of the keys on 
conventional keyboards. Within the area of the harmonic tones 
(n,m=4,5,6,7) this type of key can continuously have the aforementioned 
maximum width. This type of key has a central section of reduced width, 
preferably half the maximum width, at least within the area of the melodic 
tones (m,n=8 to 15). A second type of key which is recessed against the 
first type of key is arranged within this tone area, whereby the recessed 
keys have their largest width in the central area of the first mentioned 
type of key, and their width is strongly reduced in the rear section of 
the field of the chromatic tones (n,m=16 to 32) located adjacent to the 
melodic tones, whereby the section with strongly reduced width lies 
adjacent to a correspondingly smaller section of the first mentioned type 
of key as well as a third type of key which is constructed similar, 
preferably equally narrow. 
At least within the area of chromatic tones, the first type of key thus 
comprises keys with a frontal area of maximum width, a central area of 
reduced width, preferably half the maximum width, and a rear section with 
a further reduced width that preferably corresponds to a quarter of the 
maximum width. The second type of key has two differently wide areas at 
least within the area of the chromatic tones, namely a frontal width that 
preferably corresponds to half the maximum width, and a rear section of 
reduced width that preferably corresponds to a quarter of the maximum 
width. As compared to these two types of keys, the third type of key which 
is exclusively arranged within the area of chromatic tones preferably has 
one single width, namely a width that corresponds to a quarter of the 
maximum width. 
Finally, keys for the microchromatic tones (n,m=33 to 64) can adjoin the 
area of chromatic tones, that is, preferably arranged to the right of the 
keys that correspond to the chromatic tones. These keys which preferably 
have a width which corresponds to an eighth of the maximum width are 
preferably constructed as sensors and lie in a preferred doubled example 
of the aforementioned keyboard structure within the area of the recessed 
sections of the keys assigned to the harmonic tones. 
The keys of the keyboard according to the invention thus provide the 
possibility of playing natural tones in series. All keys preferably have 
the same height; this means that no key protrudes over another one, so 
that glissando playing can be performed. 
The wedge shape of the keys suggested according to the invention in the 
tapered area ensures an even distribution of the playing surfaces and in 
turn provides substantial advantages in regard to the performance 
technique. 
While the keyboard of the keyboard instrument according to the invention is 
preferably a manual, which means a keyboard that is played manually, it is 
basically also possible to utilize this keyboard with keys activated by 
the feet as is customary with an organ. 
While a scale change can be executed by activation of a push button in the 
conventional manner (see keyboards of electronic keyboard instruments), 
the keyboard instrument according to the invention utilizes a second 
manual which is structured similar to the first manual and into which the 
new fundamental can be entered. Both manuals can be switched parallel with 
the aid of a special coupler. 
The additional manual furthermore makes it possible not only to quickly 
change the scales, but also to arbitrarily combine the manuals during 
simultaneous play, which in turn provides a substantial expansion for the 
playing of natural tones. It is, for example, possible to not only combine 
two overtone series with m=1,3,5,7,9,11,13,15, in any desired manner, but 
also to combine overtone and undertone series with each other by switching 
one manual to the undertone series; thus the following combinations are 
possible: 
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1) I: Overtone series 
3) I: Undertone series 
II: Undertone series II: Overtone series 
2) I: Overtone series 
4) I: Undertone series 
II: Overtone series II: Undertone series 
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Even couplings between the manuals are possible. This means that altogether 
140 combination possibilities can be realized. 
An octave shift of the tones on one manual of the keyboard instrument 
according to the invention is preferably made possible by depressing a 
special key. A reversal of the fundamentals can be particularly easily 
realized, whereby the fundamental is, for example, octave shift on one of 
the manuals (for example the lower manual). One adjusting wheel per manual 
is furthermore provided in order to quickly shift the instrument. This 
means that the tonal range of the instrument can be enlarged without any 
problems, whereby the distances can be increased by octave shifts if 
undesirably dense sound combinations of different scales occur. 
Surprising sound effects can be obtained by the addition of 
pre-programmable mixtures. By entering 3-3-2, the tone played is 
supplemented by overtones within the predetermined intervals; the 
following sound combinations can be played: 
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tone played 8 9 11 10 
11 12 14 13 
14 total sound 
15 17 16 
16 17 19 18 
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Mixtures of both manuals can furthermore be combined or coupled with each 
other. 
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16 
8 22 
1st manual 11 24 8 2nd manual 
m = 2 14 28 10 m = 3 
18 30 13 
36 16 
39 
48 
total sound 
______________________________________ 
Undertone scales are thus far used relatively little in compositions 
because of the lack of suitable keyboard instruments. The keyboard 
instrument according to the invention allows a practical realization of 
undertone scales whose melodic tone series can be recognized, although 
they are ficticious when played polyphonically. Since the same keys can 
basically be utilized for the undertone scales, all that is really 
necessary is to alter the colors of the keys. While the harmonic keys 
third and seventh are for example, normally blue and green, the lower tone 
series can be indicated optically, for example, by the fact that the two 
aforementioned keys remain blue, while the seventh of the overtone or 
undertone series is underlaid with yellow which can, for example, be done 
by an appropriate illumination of the keys. 
The invention is described in detail in the following with the aid of the 
figures. They show:

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The keyboard illustrated in FIG. 1 comprises a lower manual (1) as well as 
an upper manual (2), a collective adjusting wheel (3) for the fundamental 
frequency f.sub.o of both manuals with a corresponding display (3a), a 
flip switch (4) in the left area of the lower manual (1) as well as a flip 
switch (5) in the left area of the upper manual (2) in order to switch the 
corresponding manual to the overtone or undertone series, and a coupling 
switch (6) which is arranged between the upper and the lower manual and 
makes a coupling of both manuals possible. For octave shifts one adjusting 
wheel (11 or 12) is provided per manual (1,2). At the right end of each 
manual (1 and 2), equally structured keyboard fields (7 or 8) are provided 
in order to preset certain mixtures that are displayed on display units (9 
and 10) arranged above the keyboard fields (7 and 8). The key fields in 
the example shown in the figure are designed as a ten-key keyboard. 
Modulation keys (13) are arranged below the keys of the upper and lower 
manual (1 and 2), and the numbering of the modulation keys (see also FIG. 
2) corresponds to the modulation factor m. Four not closer specified 
fields (A, B, C, D) for programs, samplers, sound synthesis and so forth 
are arranged above the upper manual (2) within a framed area. 
FIG. 2 shows a detail of, for example, the lower manual (1) in the area of 
the keys assigned to the chromatic natural tones in order to illustrate 
the shapes of the keys. 
FIG. 2 furthermore shows that three different types of keys are utilized, 
namely the keys (20-23) which extend over the entire depth of the 
corresponding manual, recessed keys (30-33) with smaller dimensions than 
the first mentioned keys, as well as even smaller keys (40-43) arranged in 
the rear area of the manual. 
The large keys (20-23) comprise a frontal section (24) with a given maximum 
width, a central section (25) with half the maximum key width, and a rear 
section (26) with a quarter of the maximum width. Tapered areas (27 and 
28) with slanted lateral edges are arranged between the three 
aforementioned areas (24-26) . 
The next smaller keys (30-33) extend with their frontal section (34) 
between two adjacent central sections (25) of the large keys (20-23) and 
have a recessed or rear section (35) that borders two adjacent keys 
(40,40; 41,41; 42,42) of the smallest type. The medium sized keys (30 to 
33) have a frontal pointed section (37) that borders the slanted edges of 
the tapered sections (27) of keys (20 to 23), as well as a rear narrow 
section (36) that borders the frontal pointed sections (46) of the rear 
keys (40 to 43). The medium sized keys (30 to 33) have the same width in 
the frontal section (34) as the adjacent central sections of keys (20 to 
23) with whose sections they are arranged alternately. The rear keys (40 
to 43) as well as the rear key section (35) have the same width as the 
rear section (26) of the large keys. 
The following series results in the rear key field: large key (section 
26)--rear small key 40 (41, 42, 43)--medium sized key (rear section 35). 
FIG. 3 illustrates how an overtone series or a natural tone series is 
played on the keyboard instrument in the natural tone system, namely in 
the series of the key numbers (1 to 64), in accordance with the natural 
tone numbers. 
FIG. 3 furthermore illustrates that harmonic tones can be played in the 
left field with the key numbers (4 to 7), that the melody-forming tones 
can be played in the central field with the key numbers (8 to 15), and 
that the chromatic tones can be played in the upper field with the key 
numbers (16 to 31). In the last octave the key numbers (33 to 64) which 
are assigned to the microchromatic tones of the same numbers are arranged 
adjacent to the aforementioned keys. 
16 tones can be played in each octave, which does not counteract the 
playing of music in the natural tone system since the natural tone system 
can also be expanded downward in an unlimited manner. If one plays, for 
example, the chromatic tones (16 to 32) in the lowest octave, then the 
fundamental must be visualized four octaves lower, which means outside the 
instrument offset towards the left in FIG. 1 and FIG. 3. 
The previously described keyboard or the previously described manuals are 
specially adapted to the playing of natural tones by the fact that the key 
widths and arrangements meet with the requirements of the natural tone 
series, which means that the intervals become constantly smaller, and the 
boxed arrangement of the keys in particular in the area of the chromatic 
tones represents a technological peculiarity that enhances the ability to 
play the keyboard instrument.