Topics range from species counterpoint through post-tonal and beyond. See also the Dictionary of Digital Media.

a
- Absolute music
- Accelerando
- Accented passing tone
- Acciaccatura
- Accidental
- Accompaniment
- Acoustics
- Adagio
- ADAT
- Added-note chord
- Added values
- Additive rhythm
- Additive synthesis
- Aggregate
- Agogic accent
- Aleatoric
- Al fine
- Alla breve
- Allargando
- Allegro
- All-interval row
- Al segno
- American Federation of Musicians
- Ametric
- Analog synthesis
- Andante
- Anhemitonic pentatonic scale
- Answer
- Anticipation (ANT)
- Antiphon
- Antiphonal
- Applied dominant
- Appoggiatura (APP)
- A&R
- Arch form
- Arpeggio
- Arranger
- Articulation
- Artist
- Artist management
- Ascending
- Assignment
- Asymmetric meter
- A tempo
- Atonality
- Augmentation
- Augmented interval
- Augmented triad
- Aural
- Authentic modes
- Auxiliary tone