r in music is brought about chiefly through their
use.]

The most important means of gaining unity and coherence in a
composition is to have it written in a clearly defined tonality,
especially at the outset. This definite tonality is the "centre of
gravity," so to speak, about which the whole composition revolves. If
this tonal centre were uncertain or wandering, we should have a
feeling of vagueness and perplexity which, except for special dramatic
effect, is never found in works of the great composers. Thus we speak
of a Symphony in C minor, of a Quartet in F major and of a Sonata in
B-flat minor;[46] this foundation key being comparable to the basic
color-scheme of a painting. There is also a particular aesthetic
effect and color-appeal associated with each key; and the listener
should train himself to be sensitive to the brilliance of such keys as
D major and E major, the richness of B major, the dignity of E-flat
major, the almost cloying sweetness of D-flat major and of G-flat
major and the tragic depth of B minor and G minor. No piece, however,
should remain for long in the same key; for music cuts so deeply into
the consciousness that there would result an intolerable monotony.[47]
Even in the simplest folk-songs, therefore, we often find manifested
an instinct for those changes of tonal centre which are technically
called "Modulations." All the keys founded on the twelve semitones of
the chromatic scale are related--though in varying degrees of
closeness; and in modern music, no matter how complex the modulations
often sound, we may be sure that the composer plans them as carefully
as the painter adjusts his color-scheme. For definite acoustical[48]
and harmonic reasons, however, the keys most closely related to a
given tonal centre are those situated a perfect fifth above--the
Dominant; a perfect fifth below--the Subdominant; and the Relative
Minor, the key-note of which is a minor third below, _e.g._, A minor
in relation to C major, C minor to E-flat major. The relative minors
of the Dominant and Subdominant also bear a close relationship to a
given tonic; and into these _five_ keys is made a large majority of
the modulations in any piece of music.[49]

[Music:

Subdominant Tonic Dominant

Relative Relative Relative
Minor Minor Minor]

[Footnote 46: As for example the famous one of Chopin.]

[Footnote 47: Even great composers have at times made this mistake,
_e.g._, Mendelssohn