I cannot help but comment this - I am glad this thread gave folks the opportunity to "geek out" (gave me a bigger chuckle when Chic's "Le Freak (Freak Out)" popped into my head).
@Noel - Thank you for the file. A question came to mind for me in that the constraint of "cannot have 2 or more consecutive semi-tones" alone adds serious constraints to a "permutation;" so much so that I would have simply attacked it with a piano keyboard at first. The wording of the question did not make sense till I saw the pdf, and I was curious if that approach was ever considered? Ironically I am often intrigued by the interactions between pure mathematicians (theory) and engineers (application); I guess this is why I chose physics as my undergrad.