The used music files "funktest.sid" and "unleash.sid" are examples from GoatTracker V2.73 
(see http://csdb.dk/release/?id=152420) and were release as an itegral part of that GPL licensed project. 

The music files "LMan - Vortex.sid" and "LMan - Confusion 2015 Remix.sid" where created by Markus Klein (see 
http://markus-klein-artwork.de/sid/) and are used here with his specific permission.