which Android version are you using, because there has been changes in the Android API regarding the hardware volume buttons?
Basically you should try to keep the sampling rate and bitrate as low as possible while it still sounds good, as described in the Performance Hints doc of BackgroundMusic: http://v-play.net/doc/vplay1-backgroundmusic.html#performance-hints.
However, if your sound file does not seem to work on Android that might be a sound playing issue. Could you send us your zipped project which only contains the testing of playing the sound files that work, or do not work please?
Regarding the volume: ist there any chance you did set the volume of another Sound or BackgroundMusic item to 0 before? Actually, that property affects all of the Sound items and not only one instance of it.