Editors having music is a bit unusual in the first place. My suggestion would be disable music in the editor; users can easily play music in the background using their usual music app.
Alternatively, have a jukebox in the player that plays music in Lix's music folder. I suspect the level selection file browser can mostly be re-used for this, with just a few changes needed; media control buttons - only really needs Play, Pause, Stop, and maybe a selection between continuous, shuffle and repeat 1 - instead of "Play", preview, etc. (Why repeat 1? This might just be me, but I often like to, while making a level, have the music it'll have playing in the background. If no Lix users share this sentiment, disregard.)