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=USUAN1100800

MacLeod's description:

Genre: Classical
Length: 4:19
Instruments: Voice

Based on 11th century sacred music, this pieces carries melodies only, and no words.
ISRC: US-UAN-11-00800
Calming, Mystical, Somber, Uplifting 2011