A notation defining how many beats are in each bar and which note value counts as one beat; almost all dance music uses 4/4.
A time signature is a pair of numbers written at the start of a piece of music: the top number states how many beats fit in one bar, and the bottom number indicates the note value that equals one beat. Dance music produced for DJs is overwhelmingly written in 4/4, meaning four quarter-note beats per bar, which is why phrases and transitions are counted in multiples of four.
Why it matters
Understanding that a track is in 4/4 tells you where the downbeat lands, how to count phrases, and why transitions are planned across 8, 16, or 32 bars. A track in an unusual time signature such as 3/4 or 6/8 will not phrase correctly when mixed against a 4/4 track, and sync or quantize features will be unreliable.
