Singing using solfa syllables to denote the notes of the scale of C major WordNet 3.0 & Open English WordNet

In music, solfège or solfeggio, also called sol-fa, solfa, solfeo, among many names, is a music education method used to teach aural skills, pitch and sight-reading of Western music. Wikipedia

A pedagogical solmization technique for the teaching of sight-singing Wikipedia Disambiguation

System of describing and teaching notes of a musical scale Wikidata

A method of sight singing music that uses the syllables do (originally ut), re, mi, fa, sol (or so), la, and si (or ti) to represent the pitches of the scale, most commonly the major scale. The fixed-do system uses do for C, and the movable-do system uses do for whatever key the melody uses (thus B is do if the piece is in the key of B). Wiktionary