time signature

The time signature (also known as meter signature) is a notational convention used in Western musical notation to specify how many beats are in each measure and which note value constitutes one beat.

In a musical score, the time signature appears at the beginning of the piece, as a time symbol or stacked numerals (such as  or 3/4) immediately following the key signature (or immediately following the clef if the piece is in C major, A minor, or a modal subset). A mid-score time signature, usually immediately following a barline, indicates a change of meter.

There are various types of time signatures, depending on whether the music follows simple rhythms or involves unusual shifting tempos, including: simple (such as 3/4 or 4/4), compound (e.g., 9/8 or 12/8), complex (e.g., 5/4 or 7/8), mixed (e.g., 5/8, 3/8 or 6/8, 3/4), additive (e.g., (3+2+3)/8), fractional (e.g., 2½/4), irrational meters (e.g., 3/10 or 5/24), or other meters.