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.