I have found one in my old blitzmax folders. It was written by Alan MacDonald way back when blitzmax was fairly new, but I think it might still work. I have used this a few years back for playing mod tunes, so at least it worked back then. I have attached the code. To use it you unpack the folder and copy it to the module folder of blitzmax and then import the module.
 You will need to download the bass.dll from somewhere and put that in the folder of your blitzmax project.