This article is from the Theatre FAQ, by aku@leland.Stanford.EDU (Andrew Chia-Tso Ku) with numerous contributions by others.
This really isn't a FAQ, but misuse of the term "soundtrack" is
so common on r.a.t and irksome to regular readers that this note
is included in FAQ document. A "cast recording" is the audio
recording of a *stage* musical (or play for that matter), while
a "soundtrack" refers to the recorded score of a *movie*. Other
definitions can be found, but this is the generally accepted
convention in r.a.t, and repeated use of "soundtrack" may
provoke criticism - you've been warned!