This is an Italian slasher film, or Giallo, from the 80s. Its about a guy who escapes a mental institute and traps the cast of a play inside the theater, offing them one by one.
Nothing original really, but the play they are performing and music I think is sort of Steinmanish. The music in the film sounds a bit like Nowhere Fast/Faster than Speed of Night, and the play itself features an angel playing the sax, a bunch of dudes dancing around for no real reason...
Anyway, good flick if you like that sort of thing. Here is an image of the killer:
http://www.horrordvds.com/reviews/n-z/sfright-ab/sfright-ab_shot2l.jpg
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