This is the boss music that plays during the bossfight with Rekka. The original song was produced by The Flaming Lips, but Elsinore covered it for the version you hear ingame.

This was created using files stitched together from the game, including the cutscene bits. Keep in mind the bridge to Verse 2 has two versions - one of which plays when you're on any difficulty Hard or above (I think). It's essentially the same, but with an extra note to the guitar solo to correspond to Rekka throwing more pipes. This video uses the hard+ version.

This video, if not taken down by copyright ID or something, will be deleted if/when the music is added to streaming services. I'm only uploading this because they haven't released the track yet.

Timestamps (Hoping Chapters starts working at some point...):
00:00 - Intro
00:55 - Verse 1
01:56 - Chorus 1 Bridge
02:30 - Chorus 1
02:57 - Verse 2 Bridge
03:27 - Verse 2
04:22 - Chorus 2
05:02 - Outro