The only thing that seems to be missing from GDevelop is a simple music sequencer to allow the creation of simple tunes. I am wondering if there is a plugin like Piskel or JFXR that could be bundled so that when you add music you get the option to upload or create a tune. It could be a very simple 8bit sequencer with 3-4 channels. @SilverStreak suggested http://boscaceoil.net/ but there may be other candidates…
Thoughts?
From a quick google, here are some other options:
Maybe they can make there own original one, here me out though. It’s gonna probably be really simple. maybe 8-bit or 16-bit (maybe both) since it might be hard to code. But again, you can probably just go online and download/use free music tools. It may be a bit of a hassle, but again, its simple.
I think simple is the key - we don’t meed a 16 channel midi sequencer with high quality samples etc. Just some basic midi sounds with a few channels so you can have rhythm, bass, chords and melody 
After some digging, looks like this is already on the Trello board:
Might be worthwhile voting that up.