Sample volume problems

I want to control the volume of my samples. But it makes trouble. Giving every sample its channel causes my mainsong to stop randomly when another sample is playing. And telling the samples to set to this and that volume causes some samples sometimes to play at 100% instead the given value.

Somebody had this problem before? Any advices?

Ah, nevermind. I had forgotten to change one event, which turned off my song then for the channels solution. Now this solution works :)

Nevertheless curious why the first method with setting the sample volume directly fails sometimes.