Time signature

A time signature (also known as meter signature, metre signature, and measure signature) is an indication in music notation that specifies how many note values of a particular type fit into each measure (bar). The time signature indicates the meter of a musical movement at the bar level. In a music score the time signature appears as two stacked numerals, such as 44 (spoken as four–four time), or a time symbol, such as or (spoken as common time or cut time, respectively). It immediately follows the key signature (or if there is no key signature, the clef symbol). A mid-score time signature, usually immediately following a barline, indicates a change of meter. Most time signatures are either simple (the note values are grouped in pairs, like 24, 34, and 44), or compound (grouped in threes, like 68, 98, and 128). Less common signatures indicate complex, mixed, additive, and irrational meters.