A capella - unaccompanied vocal music.

Accelerando - (Italian: becoming faster) is a term to show that the music should be played at an increasing speed.

Accent - placed above a note to indicate stress or emphasis

Accidentals - sharps, flats, or naturals, which are not found in the key signature.

Accordion - a musical instrument which includes a keyboard for the right hand. The tone or sound is produced by the bellows which act upon metallic reeds.

Acoustics - the science of sound.

Adagio - (Italian: slow) Slow; slower than andante, faster than largo.

Al fine - to the end.

Allegro - very quickly, although not as fast as Presto.

Al segno - return to the sign.

Alto - generally used to refer to the lowest female voice.

Andante - a movement in moderate time.

Andante grazioso - slowly and gracefully.

Animato - animated and lively.

A tempo - in time.