A. Acapella - any singing performed without instrumental backing.
B. Acoustic Music- a music that solely or primarily uses instruments which produce sound through entirely acoustic means, as opposed to electric or electronic means.
C. Ambient music - music that can either be listened to intently, or be played in the background and easily be ignored. oftentimes used for relaxation and meditation.
D. Ballad - generic term for usually slow, romantic, despairing and catastrophic songs