A2 (music)

In music, a2 is an abbreviation for a due or à deux. The marking signifies that two instruments are to play the designated part in unison. It is generally marked after a previous marking of solo, when multiple performers are looking off of a singe sheet of music.

An example of this would be after a flute solo. If there were three flute parts, but only two are required to play, "a2" would be marked. If, later on, all three flutes were then needed, "a3" would be marked, or "unis" if they were all to play the same.

This would be used when quieter instruments would be playing against a full orchestra, instructing more instruments to play the same part to balance the sound. It would also be used in smaller ensemble music, for example, a quartet. If there were three instruments to a part, but one part needs to be louder than the others, the other parts may show "a2".