Evan McCandless, the guy who made the lovely simpleplanes OST is a bassist in that band. I found out that this bands music style is actually very, very similar to the SimplePlanes OST style.
So I play their songs in the background while playing SP, and unlike playing other songs, this doesn't disturb the immersion into the game! If you have grown accustomed to the original, repetitive, SP tracks I recommend this! It fits so well! Devs, if in future you add more music, don't stray from this great source of music!