From Video Game Music Preservation Foundation Wiki
Thanatos is only song in the game Thanatos. It was composed by Julian Breeze and plays after the title screen, during the credits and the main menu.
Thanatos (CPC)Julian Breeze worked on the ZX Spectrum and Amstrad CPC ports simultaneously, so probably neither port has the "original" version of the song, and they both sound similar.
This port rendered the music on the AY-3-8912.