A

(1) Name of a note, or a Pitch Class; see also Pitch names. It is the 6th degree in the scale of C major, and is usually taken as the standard for tuning, a′ =440 cycles per second (or Hz) being the normal concert level; see Pitch.

(2) The Italian word a is used in music as a preposition, e.g. ‘a 2’, to mean ‘in two voices’. In early music it refers to the number of voices in a polyphonic work; in scores after 1700 ‘a 2’ means that two instruments play a single line together. The French equivalent is à.