I bet I know people who've bought this!

To be fair, though, it's no dafter than buying a CD about bodhran playing or DADGAD guitar accompaniment. Like any supposedly 'simple' instrumental skill, cajun triangle is easy to do badly and hard to do well. The best player I ever heard was my old colleague in Ti-Fer Cajun Band, Clare Gilliam. Always enjoyed playing with her and it never felt like hard work but there was a fair bit of work involved.

Though I suppose the other possiblility is that the CIA have commissioned this as some sort of interrogation aid. 'Come on, Mustafa. Tell us where the Semtex is or it's another two-step for you!'