Every rule has its reason and its consequences.  St. Augustine, who knew the Beautiful, of which art is only the expression, and who could explain it well, has given us a brief but admirable definition of music:  “Music is a succession of sounds each calling forth the other.”  Simple yet profound words!  The sounds call each other forth, desire and mutually attract each other, and in every age this attraction has been so clearly evident, that the seventh note in the scale, when it meets the others each of which has its particular name relating to its particular function, tonic, dominant, etc., is simply called the sensitive note, from its tendency to pass into the atonic.

Passional trueness is based upon this tendency of the notes to pass into those which succeed them, and upon this reciprocal attraction of sounds.  Thus, notes, which have a tendency toward the acute or shrill, may be raised two commas or more above temperate trueness.  Notes which have a tendency toward the grave may be lowered in the same proportion.  (Example, taken from “The Prophet,” by Meyerbeer.)

    Ex.  No. 1.
    [Music]
    Ah! mon fils

    Ex.  No. 2
    [Music]
    il re-nia ta me-re

Here, the B may be but two commas distant from the C; and in the second example given, the A flat may also be but two commas removed from the G, and this change far from producing a disagreeable effect upon the ear, will make a most striking impression and the accent will be far more dramatic than before.  Try the reverse, that is, divide the interval B sharp-C into seven commas on the semitones A flat-G; it will be unendurable.  Whence we may deduce the fact that to sing false is to sing above or below a note in the inverse direction to its attraction.

Delsarte, in his definition, speaks only of the semitone, and we ourselves give examples of that sort of attraction only; but it does not follow that the other intervals are not equally subject to the same law.  Their attraction may not be shown by the same effects.

The master added, in speaking of trueness in singing:  “The triad is the breathing-place of the tonality; the notes composing it should be absolutely true.  They are the singer’s invariable and necessary law.  They characterize repose.  Their office is that of attraction, and they can only be attracted mutually, with the exception of the tonic, which is the centre of attraction not only for various notes, but for the phrase and the entire composition.”

Delsarte was very severe in regard to those who sang false; but to sing true was not, to his thinking, a good quality.  He said, on this point, that no one would compliment an architect because he had built a house in accordance with geometrical rules.  Whence he concluded that trueness is the least of good qualities, and the lack of it the greatest of vices, and he added in regard to style:  “The most important quality is expression, and a lack of expression is the least of vices.”