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=USUAN1100063

MacLeod's description:

Genre: Soundtrack
Length: 0:40
Instruments: Small Ensemble - Harpsichord, Bass

Harpsichord in tritones with a bass pedal. 035
ISRC: US-UAN-11-00063
Dark, Unnerving, Mysterious, Eerie 2006