How I Did It
Tools I Used
Cubase 5, Melodyne, Stylus RMX 1.8, Omnisphere, Korg m3, Gretsch hollowbody guitar, NI Guitar Rig 2
Original Samples
the guitar parts
Process
Once I figured out the scale of the gregorian chant, I used Melodyne to make the melody by Kaer Trouz fit that scale. The part I used from Kaer's song was a relatively freeform part from the opening of her song, which didn't adhere to the BPM very tightly, so I sliced and re-assembled that a bit to make it sit tighter with the beat. Everything else was pretty standard remixing technique.
Other Notes
I was totally blown away how well Kaer's singing works with such a different scale. Amazing...