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=USUAN1100378

MacLeod's description:

Genre: Horror
Length: 1:23
Instruments: Synth

Just a very low note (a C) to be used as a bed for any very unnerving and dark scene. 037
ISRC: US-UAN-11-00378
Dark, Eerie, Mysterious, Unnerving 2007