A madrigal is a secular vocal music composition of the Renaissance (15th–16th c.) and early Baroque (1600–1750) eras. The polyphonic madrigal is unaccompanied, and the number of voices varies from two to eight, but usually features three to six voices, whilst the metre of the madrigal varies between two or three tercets, followed by one or two couplets. Unlike the verse-repeating strophic forms sung to the same music, most madrigals are through-composed, featuring different music for each stanza of lyrics, whereby the composer expresses the emotions contained in each line and in single words of the poem being sung.