Protecting a sound channel

I've nearly finished my first game in Blitz :) However i'm having some trouble adding some of the final polish to the game, specifically the background music.

I have set the music up to loop and played it, but after a while the music stops, I think because the sound channel is in use by another sound.

music=LoadSound("<filename>")
LoopSound music
PlaySound music

Is there a way I can protect the music entity so that it always plays regardless of other sounds please?

Assign the sound to a sound channel:

music=LoadSound("<filename>") 
LoopSound music 
chnBackground=PlaySound (music)

Then you can check to see if the channel is still playing

If ChannelPlaying(chnBackground) = false then
   PlaySound music
End If