MI: LIBRARY: THEORY: BASICS: ANACRUSIS

Compositions don't always begin on the first beat of the first measure.  One or several notes can occur beforehand.  This note is called an anacrusis.  (Also known as an 'upbeat' or 'pick-up note'.)

Normally, the number of beats or the fraction of a beat used in the anacrusis is subtracted from the last measure of the work.