Music by Kevin MacLeod (original composer: Pyotr Ilyich Tchaikovsky). Available under the Creative Commons Attribution 3.0 Unported license. Download link: https://incompetech.com/music/royalty-free/index.html?isrc=USUAN1100019
MacLeod's description:

Genre: Classical
Length: 5:40
Instruments: Piano

Opus 40; Number 9. Written 1878. Recorded 2005. 008
ISRC: US-UAN-11-00019
Dark, Unnerving, 2005