Hello FelinaLain !
The music actually comes from an asset pack (that we paid for and have the rights to use without credits), called "Ultimate Game Music Collection", by John Leonard French. You can find the concerned song here : https://soundcloud.com/game-music-collection/arid-wasteland
The music in Supraland must come from that asset pack too.
But you're right, we should've credited it anyway, so here we go !
Have a good day.