striking characteristics is its use of whole-tone progressions, a
natural result, of course, of its dependence upon the old modes. Other
contemporary Frenchmen have made occasional use of Gregorian effects;
but Debussy was the first to adopt them deliberately as the basis of a
settled manner of utterance, and he has employed them with increasing
consistency and devotion. His example has indubitably served to enrich
the expressional material at the disposal of the modern
music-maker--there cannot conceivably, in reason, be two opinions as to
that: he has acted upon a principle which is, beyond question,
liberating and stimulating. And the adaptability to his own peculiar
temperament of the wavering and fluid order of discourse which is
permitted by the flexibility and variety of the antique modes is
sufficiently obvious.

His resort to Gregorian principles is, it has been observed, far from
being a matter of recent history with him. Almost twenty years ago we
find him writing in the spirit of the old modes. Examine the opening
phrases of his song, _Harmonie du Soir_ (composed in 1889-1890), and
note the felicitous adaptation to modern use of the "authentic" mode
known as the Lydian, which corresponds to a C-major scale with F-sharp.
Observe the use of the same mode in the introductory measures, and
elsewhere, of his setting of Verlaine's _Il pleure dans mon coeur_
(1889), the second of the "Ariettes." Five years later, in _Pelléas et
Mélisande_, the trait is omnipresent--too extensive and obvious, indeed,
to require detailed indication. One might point out, at random, the
derivation from the seventh of the ecclesiastical modes (the Mixolydian)
of the phrase in the accompaniment to Arkël's words in the final scene,
"L'âme humaine aime à s'en aller seule;" or the relationship between the
opening measures of the orchestral introduction to the drama and the
first of the "authentic" modes, the Dorian; or between the same mode