Why are they called Schrage Musik?

[Stephan Wilkinson]

For decades, I've read and heard that "Schrage Musik"--the upward-slanted guns on Luftwaffe night fighters--was translated into English as "jazz music." That never made any sense to me. What did guns have to do with jazz? "Well, jazz was forbidden in Germany," I was told. (Actually it wasn't, but never mind...)

Huh? Forbidden guns?

So tonight I looked into a German/English dictionary and discovered that the word Schrage (I can't figure out how to inset the proper umlaut, sorry) means "oblique," or "slanted." Which makes perfect sense: the guns are mounted at an oblique, slanted angle to the fuselage. So the guns are slanted, and their fire is music, at least to the attacker.

Where did the "jazz music" nonsense come from?