This is a BEEPER / 1-bit chiptune entitled "Through the heavy fire"
composed in 2013 by MISTER BEEP, especially for the best
musical instrument in the world: ZX Spectrum 48K / Timex Computer 2048. 

Many thanks for Introspec for all the coding-help!!!

MISTER BEEP
http://mister_beep.republika.pl/
http://1bit.i-demo.pl/