Time signature
A time signature (also known as meter signature, metre signature, and measure signature) is a convention in Western music notation that specifies how many note values of a particular type are contained in each measure (bar). The time signature indicates the meter of a musical movement.
4 time signature. The time signature indicates that there are three quarter notes (crotchets) per measure (bar).
In a music score the time signature appears as two stacked numerals, such as 4
4 (spoken as four–four time), or a time symbol, such as (spoken as common time). 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 2
4, 3
4, and 4
4), or compound (grouped in threes, like 6
8, 9
8, and 12
8). Less-common signatures indicate complex, mixed, additive, and irrational meters.
4, also known as common time (); 2
2, alla breve, also known as cut time or cut-common time (); 2
4; 3
4; and 6
8