I'm just looking at a project, utilising a Raspberry Pi, where I need to have three separate music tracks being played simultaneously and out of separate channels (assuming that the RPi can handle three separate audio output devices being connected at the same time - that's another question in another forum).
I haven't selected a Lazarus module for this yet, but have seen both UOS and PlaySoundPackage for using to play music files in Lazarus.
Oh, and it needs to be controlled via RS232...but, again, that's a separate issue (and I've already managed to write some code to send/receive data over RS232 in Lazarus).