Calling non-ZXB code with RANDOMIZE USR

[LTee]

Hi all, it's been a while but I've been kind of busy. :-)

My game project is almost complete, I just wanted to add some music. I wrote a couple of (quite bad) tunes with Beepola, compiled with the Music Box engine. I've loaded these high into memory (64000 up), well away from my ZXB code and I'm calling them with 'randomize usr X' from within ZXB. The player is configured to play the tune once and then return control to the caller.

I'm having a small problem that I can get around, but I wanted to ask about. If I call the music player from within a SUB or a FUNCTION, the Spectrum crashes after playing the tune. If I call it from OUTSIDE a SUB or FUNCTION (i.e. just from within the main code) then it returns fine.

For example:

Code:

cls
pause 0
print "test"
randomize usr 64000
pause 0
print "test 2"
test()
stop

SUB test()
    randomize usr 64000
END SUB

In the above code (surmising that the player is loaded at 64000), the tune plays and returns correctly after "test" is printed, but crashes after playing the tune after "test2" is printed.

Is calling external code via "randomize usr" actually supported? It's not in the Wiki, so I'm thinking 'not'. If it is supported, is there something else I should be doing before making such a call? Or is there a better way of doing this?

My main concern is that the call which appears to be working is actually doing something bad that I'm just not seeing immediately and might cause unexpected problems later.

Thanks for any insights! :-)