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and were employed only as auxiliary notes or connecting links, rather than structural or cadential notes, so that the gaps, though covered up, were not concealed. And it was left to the art-musician to take the final step and evolve the 7-note scale of which every note could be used with equal freedom and certainty.
Of the tunes in this volume, some are pentatonic; others belong to the transitional period and are hesitatingly hexatonic, or even heptatonic; while a few are frankly in the major mode, i.e. diatonic 7-note tunes in which no indication of a pentatonic origin can be traced. For the benefit of those interested in this technical question, particulars concerning scale and mode are given at the head of every tune in the text. The names and characteristics of the 7-note diatonic modes need no explanation; but with regard to the pentatonic modes, which are but rarely employed by art-musicians, it may be as well, perhaps, to explain the method of classification and nomenclature adopted in this volume. This is set out in the chart on the opposite page.
The five pentatonic modes there given have been derived in the following way:—
If from the white-note scale of the pianoforte the two notes E and B be eliminated we have the pentatonic scale with its two gaps in every octave, between D and F and between A and C. As each one of the five notes of the system may in turn be chosen as tonic, five modes emerge, based, respectively, upon the notes C, D, F, G and A. The gaps, of course, occur at different intervals in each scale and it is this distinguishing feature which gives to each mode its individuality and peculiar characteristic.
The one-gapped or hexatonic scale, and the 7-note or heptatonic scale are, as we have already seen, derivates of the original pentatonic, obtained by the filling in, respectively, of one or both of the gaps. Miss Gilchrist (see Journal of the Folk-Song Society, v., pp. 150-153), whose very clear exposition of this matter I am in the main following, allows the lower gap, i.e. between D and F, to be completed by the insertion of either E-flat or E-natural, and the upper gap, i.e. between A and C, by the addition of B-flat; and by this method she has succeeded in classifying very satisfactorily her material, which consists entirely of Gaelic tunes. When, however, I came to apply this method to the mountain-tunes I found it necessary to make the following modification, viz., to take E-natural as the constant and invariable mediate note of the lower gap, and either B-flat or B-natural of the upper. The chart, given here, has, therefore, been constructed on this plan, i.e. Miss Gilchrist's, modified in the way just explained.