Sound effects?

[LCD]

Hmm... or maybe not. Something's not *quite* right still. The music will play once, but it doesn't exit properly at the end of the tune (or if you press a key) - the Spectrum locks up rather than ending play gracefully.

I'll paste what I've been messing around with, maybe someone else can see what the issue is:

I would say, the issue is the ASM data and the RET from ASM, before PLAY_MUSIC label.
this is a procedure, so RET would not return back to BASIC but to nirvana, and the ASM datas at the end would prevent correct returning further. I faced the same problem. The solution looks so:

Code:

Procedure
  ASM Routine (without RET), JP to [ASM Label Ending] replaces RET
  [ASM label data]:
    All Data
  [ASM Label Ending]:
    Again no RET! This is empty or ending code
END Procedure