Short for tonic sol-fa, a method of teaching music, usually singing, systematized by John Curwen (1816–1880). The notes of a scale are named by syllables (doh, ray, me, fah, soh, lah, te, with the key indicated) to simplify singing by sight.

1. To sing the sol-fa syllables
2. To sing (as a melody) to sol-fa syllables