part, voice - the melody carried by a particular voice or instrument in polyphonic music; "he tried to sing the tenor part"

duette, duo, duet - a musical composition for two performers

colloquialism - a colloquial expression; characteristic of spoken or written communication that seeks to imitate informal speech

best - (superlative of `good') having the most positive qualities; "the best film of the year"; "the best solution"; "the best time for planting"; "wore his best suit"