significant feature in modern music and Debussy's example in this
respect has been highly beneficial. As to his alleged use of new
material, an astute French critic has observed that "a revolution is
merely an evolution rendered apparent." By no means all of music can
be found in nature, but the basis is there, and it remains for the
artistic imagination to select and to amplify. Already many years ago
the scientist Helmholtz said, "Our system of scales and of harmonic
tissues does not rest upon unalterable natural laws, but is partly at
least the result of aesthetic principles of selection, which have
already changed, and will change still further with the progressive
development of humanity."[293] In other words the limits of
receptivity of the human ear cannot be foreseen nor can the workings
of the artistic imagination be prescribed. The so-called Chord of
Nature,[294] consisting of the overtones struck off by any sounding
body, and re-enforced on the pianoforte with its large sounding board,
contains in epitome this basic material of music; and the several
octaves represent in a striking manner the harmonic combinations used
at different periods of development. Thus during the early centuries
nothing but triads were in use; only gradually were 7th chords--those
of four factors--introduced. Wagner was the first to realize the
possibilities of chords of the 9th, 11th, and 13th. In Debussy these
combinations are used as freely as triads, _e.g._

[Music: _Pelleas et Melisande_]

[Music: _La fille aux cheveux de lin_]

[Music: _Reflets dans l'eau_]

and he has gone far beyond anything known before in a subtle use of
the extreme dissonant elements, his sensitive imagination evidently
hearing sounds hitherto unrealized. This surmise is corroborated by
Debussy's own statement that, while serving as a young man on garrison
duty, he took great delight in listening to the overtones of bugles
and of the bells from a nearby convent. This chromatic style had been
anticipated by Chopin whose use of the harmonic series in those
prismatic, spray-like groups of superadded tones is such a striking
feature in his pianoforte works. There is, therefore, nothing outre or
bizarre in Debussy's idiom; it is but a logical continuation of former
tendencies. His works show great variety and comprise pianoforte
pieces, many songs, a remarkable string quartet, some daringly
original tone-poems for full orchestra, several cantatas, and--mos