Common metre

Common metre or common measure^[1]—abbreviated as C. M. or CM—is a poetic metre consisting of four lines that alternate between iambic tetrameter (four metrical feet per line) and iambic trimeter (three metrical feet per line), with each foot consisting of an unstressed syllable followed by a stressed syllable. The metre is denoted by the syllable count of each line, i.e. 8.6.8.6, 86.86, or 86 86, depending on style, or by its shorthand abbreviation "CM".

Common metre has been used for ballads such as "Tam Lin", hymns such as "Amazing Grace", and Christmas carols such as "O Little Town of Bethlehem". A consequence of this commonality is that lyrics of one song can be sung to the tune of another; for example, "Advance Australia Fair", "House of the Rising Sun", "Pokémon Theme" and "Amazing Grace" can have their lyrics set to the tune of any of the others. Historically, lyrics were not always wedded to tunes and would therefore be sung to any fitting melody; "Amazing Grace", for instance, was not set to the tune "New Britain" (with which it is most commonly associated today) until fifty-six years after its initial publication in 1779.