[15] The step-and-a-half (augmented second) is "unmelodic" because it is the same size as a minor third and the mind finds it difficult to take in as a second (notes representing it being on adjacent staff-degrees) an interval of the same size as a third.
[16] These syllables are said to have been derived originally from the initial syllables of the "Hymn to Saint John," the music of which was a typical Gregorian chant. The application of these syllables to the scale tones will be made clear by reference to this hymn as given below. It will be observed that this hymn provided syllables only for the six tones of the hexachord then recognized; when the octave scale was adopted (early in the sixteenth century) the initial letters of the last line (s and i) were combined into a syllable for the seventh tone.
[17] A considerable number of teachers (particularly those who did not learn to sing by syllable in childhood) object to calling the tonic of the minor scale la, insisting that both major and minor tonic should be called do. According to this plan the syllables used in singing the harmonic minor scale would be: DO, RE, ME, FA, SOL, LE, TI, DO.
There is no particular basis for this theory, for although all scales must of course begin with the key-tone or tonic, this tonic may be referred to by any syllable which will serve as a basis for an association process enabling one to feel the force of the tone as a closing point—a home tone. Thus in the Dorian mode the tonic would be RE, in the Phrygian, MI, etc.
[18] The student should differentiate between the so-called "tonality" scales like the major and minor, the tones of which are actually used as a basis for "key-feeling" with the familiar experience of coming home to the tonic after a melodic or harmonic excursion, and on the other hand the purely artificial and mechanical construction of the chromatic scale.
[19] Many other enharmonic notations are possible, altho the "five pairs of tones" above referred to are the most common. Thus E♯ and F are enharmonically the same, as are also C♭ and B, C♯ and B[double-sharp], etc.
[20] The word chromatic means literally colored and was first applied to the intermediate tones because by using them the singer could get smoother and more diversely-shaded progressions, i.e., could get more color than by using only the diatonic tones. Composers were not long discovering the peculiar value of these additional tones and soon found that these same tones were exceedingly valuable also in modulating, hence the two uses of intermediate tones at the present time—first, to embellish a melody; second, to modulate to another key.
[21] Stanford—Musical Composition (1911) p. 17.