We have, however, for this purpose a real musical material, as appears from our design. Here on a wooden form like that used for the bells, but two octaves instead of one octave long, we have arranged prisms of equal dimensions but painted black and white according to the tones they represent. Each prism shows a rectangular plate exposed to view. The plates are identical in appearance on all the prisms. They are, however, really of different lengths according to the different prisms. When these plates are struck, they give the notes of two octaves, the prisms acting as sounding boards. The sounds are soft and mellow and unusually clear, so that we do not exaggerate in describing this mechanism as really a musical instrument (resembling the Xylophone). In our design each piece is arranged in its proper position in the do major scale.
Since the intervals between the tones are the same for all the scales without distinction, if the group of prisms is moved as a whole from right to left, sliding along the wooden form, some of the prisms will fall. The resulting effect is the same as that produced when the small card was moved over the larger chart (see above). No matter how far the group of prisms is moved, the scale can be obtained by striking all the prisms corresponding to the white spaces on the wooden form.
The upper cut shows the music bars arranged for the scale of C major. The lower cut shows the transposition of the scale, preserving, however, the same intervals.
For instance, let us take away the two first prisms, do and do diesis on the left, and push the whole group of prisms from right to left until re reaches the point formerly occupied by do. If, now, we strike the plates which correspond to the notes of the major scale, we obtain the major scale in re. On examining the notes which make up this scale, we find: re, mi, fa diesis, sol, la, si, do diesis, re.
This brief description will indicate how interesting this instrument is. It contains in very simple form and expresses in a clear and delightful way the fundamental principles of harmony. Its use can be made apparent to teachers by the three following tables.
As the children derive in this way all the possible scales, they should transfer them to their copy books, making use of all the symbols of musical notation. The copying of the scales should be developed progressively: first the scale with one diesis, next the scale with two, then the one with three dieses, etc. Fine opportunities for observation are here offered. A child may see for instance that a scale with two dieses has the same diesis which appeared in the preceding scale; a scale with three dieses has the two dieses of the preceding scales, and so on. The dieses recur at intervals of five notes.
Since in using the first material, by changing the third and sixth bell, the child was taught to recognize the harmonic minor scale, to construct it and listen to it, it is now an obviously simple matter for him to make up all the minor scales.
We have thus developed exercises which prepare for the recognition of the major and minor tones as well as for the recognition of the different tones. It also becomes an easy matter to play a simple motif in different keys. It is sufficient to move the series of plates, as has been indicated, and play them over according to the indications of the white and black spaces of the wooden form.
[Transcriber's Note: You can play this music (MIDI file) by clicking on the captions.]