I got the no sound available alert.
I was trying to find a generic way to play a sound when I send a notification, as DroidScript seems to have no way to do that using standard Android stuff.
Obviously I can bundle a sound in my app but either way, I would be bypassing the main preferences and I don't want to be the only app waking the user at 4.00 am.
I suppose it's time to try the Android SDK docs and Stack Overflow to find out what I should be doing if I was using Java.
After that, I guess the alternatives are a plugin or an opt-in only user-setting with time constraints and a warning that it ignores the user's other settings.