Notation & reading
Measure
A measure, called a bar in British usage, is the span of music between two barlines, containing the number of beats set by the time signature.
The measure is the unit that makes rhythm readable: it groups beats so that a player can see where the strong beat falls without counting from the start of the piece. In 4/4 every measure holds four quarter-note beats; in 3/4, three.
Orchestral parts number measures, usually every bar or every five, so a conductor can say "from bar 61" and fifty players find the same place. Rehearsal marks, letters or boxed numbers, do the same job at structural points, and a well-prepared part has both circled.
A pickup or anacrusis at the start of a piece is an incomplete measure, and it is conventionally not numbered; the first full measure is bar 1.
Related terms
Try a short guided practice session
Read a note, try a short exercise and check your understanding. No account or microphone needed. If you want to save progress afterwards, a free account adds five instrument lessons and five theory lessons. No card.