Mezzo (Italian: half) is found particularly in the compound words mezzo-forte, half loud, represented by the letters mf, and mezzo-piano, half soft, represented by the letters mp. Mezzo can serve as a colloquial abbreviation for mezzo-soprano, the female voice that employs a generally lower register than a soprano and consequently is often, in opera, given the parts of confidante, nurse or mother, secondary rôles to the heroine, usually a soprano. The instruction mezza voce directs a singer to sing with a controlled tone. The instruction can also occur in instrumental music.