Music by Kevin MacLeod. Available under the Creative Commons Attribution 3.0 Unported license. Download link: https://incompetech.com/music/royalty-free/index.html?isrc=USUAN1100420

MacLeod's description:

Genre: Soundtrack
Length: 7:42
Instruments: Basses, Violins, Piano

Heavy effects on an arhythmic piano, and very deep bass. 037
ISRC: US-UAN-11-00420
Dark, Eerie, Mysterious, Suspenseful, Unnerving 2008