The Probert Encyclopaedia of Music

DO

In music, do is a syllable attached to the first tone of the major diatonic scale for the purpose of solmization, or solfeggio. It is the first of the seven syllables used by the Italians as manes of musical tones, and replaced, for the sake of euphony, the syllable Ut, applied to the note C. In England and America the same syllables are used by many as a scale pattern, while the tones in respect to absolute pitch are named from the first seven letters of the alphabet.