What does measure mean in music?

Notation & reading

Measure

Also: bar

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.

Time signature: A time signature is a pair of numbers showing how many of a given note value fill a bar; their grouping indicates the metre and main beats.
Rehearsal mark: A rehearsal mark is a boxed letter or number placed at structural points in a score and in every part, so a conductor can restart the whole ensemble at the same place.
Anacrusis: An anacrusis, or pickup, is one or more notes that precede the first full measure of a phrase, falling on a weak beat and leading into the downbeat.
Staff: The staff is the set of five horizontal lines on which music is written; a note’s vertical place on the lines and spaces, read against a clef, gives its pitch.

Every term in this glossary is taught in context somewhere in Arco's curricula, on the staff, on the keyboard, and on your own fingerboard at the same time.

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