The SIphonopolis sountrack has just been released:
https://store.steampowered.com/app/2127250

Just like the game's graphics, the music originates from several old projects. Some of the tracks have been remixed and/or extended.

A few small improvements to the game have been added:

• Reworked the attack of the third mid-boss in level 47.
• Machine gun hazards now make a flashing animation a second before shooting.

And finally, an easter egg of my previous game "Me and My Eldritch Parasite" has been added. Good luck finding it.