Page:A Dictionary of Music and Musicians vol 3.djvu/248

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Thus the essence of the diatonic scale was that it consisted of tones, in groups of two and three alternately, each group being separated by a hemitone from the adjoining one; and, combining consecutive intervals, any two tones with a hemitone would form a fourth, any three tones with a hemitone would form a fifth, and any complete cycle of five tones with two hemitones, would form a perfect octave.

Now it is obvious that in this series of notes, proved to be in use above two thousand years ago, we have essentially our diatonic scale; the series corresponding in fact with the natural or white keys of our modern organ or pianoforte. And as this series formed the basis of the melodies of the Greeks, so it forms the basis of the tunes of the present day.

Although, however, the general aspect of the diatonic series of musical sounds remains unaltered, it has been considerably affected in its mode of application by two modern elements—namely, Tonality and Harmony.

First, a glance at the Greek scale will show that there are seven different diatonic ways in which an octave may be divided; thus, from A to the A above will exhibit one way, from B to B another, from C to C a third, and so on—keeping to the white keys alone in each case; and all these various 'forms of the octave' as they were called, were understood and used in the Greek music, and formed different 'modes.' In modern times we adopt only two—one corresponding with C to C, which we call the Major mode, the other corresponding with A to A, which we call the Minor mode. And in each case we attach great importance to the notes forming the extremities of the octave series, either of which we call the Tonic or Keynote. We have, therefore, in modern music, the two following 'forms of the octave' in common use. And we may substitute for the Greek word 'hemitone' the modern term 'semitone,' which means the same thing.

Although these differ materially from each other, it will be seen that the original Greek diatonic form of the series is in each perfectly preserved. It must be explained that the minor scale is given, under particular circumstances, certain accidental variations [see ], but these are of a chromatic nature; the normal minor diatonic form is as here shown. The choice of particular forms of the octave, and the more prominent character given to their limiting notes, constitute the important feature of modern music called Tonality.

Secondly, a certain influence has been exercised on the diatonic scale by modern Harmony. When it became the practice to sound several notes of the scale simultaneously, it was found that some of the intervals of the Greek series did not adapt themselves well to the combination. This was particularly the case with the interval of the major third, C to E: according to the Greek system this consisted of two tones, but the perfect harmonious relation required to be a little flatter. The correction was effected in a very simple manner by making a slight variation in the value of one of the tones, which necessitated also a slight alteration in the value of the semitone. Other small errors have been corrected in a similar way, so as to make the whole conform to the principle, that every note of the scale must have, as far as possible, concordant harmonious relations to other notes; and in determining these, the relations to the tonic or keynote are the more important.

The diatonic series, as thus corrected, is as follows:—

The several intervals, reckoned upwards from the lower keynote, are—

It has been stated, however, that for modern European music, we have the power of adding, to the seven sounds of the diatonic scale, certain other intermediate chromatic notes. Thus between C and D we may add two notes called C♯ and D♭. Between G and A we may add G♯ and A♭, and so on. In order to determine what the exact pitch of these notes should be, it is necessary to consider that they may be used for two quite distinct purposes, i.e. either to embellish melody without change of key, or^ to introduce new diatonic scales by modulation. In the former case the pitch of the chromatic notes is