Muzak usally consists of, but is not limited to:
annoying, repeatitive rhythms
that horrific clapping sound every 5 seconds or so instead of drums
Muzak is generally accepted as proof that the world is doomed.
Usually renditions of classic or pop songs without the original lyrics. Management prefers this because it is cheaper and they think it is more "relaxing" than the actual songs. Derived from Music + Prozac.