What does the cryptic crossword clue "Might they take part in musical, to sing? (5)" mean?

The definition is "sing?". The wordplay uses a hidden word. Hidden in "might they take part in musicAL, TO Sing?" The answer is Altos.

Might they take part in musical, to sing? (5)

Telegraph Prize Cryptic #3022 | 27 Across | 2019-09-22 flower