I initially thought of doing this when I heard two different renditions of the combination of these two carols on Pandora, a station called Enya (Holiday) Radio (Highly recommended if you want Christmas Carols to sleep to).
I could not find the combination anywhere, but I DID find two similar ones on iTunes in the style I wanted--I Saw Three Ships by Melinda Carol and Bring A Torch, Jeanette Isabella by ProSound Karaoke.
BUT...
They were in different tempos and different keys.
So, step one, get them in the same tempo. Step two, get them in the same key (I have a tool in Audacity which, with a bit of math, does this wonderfully).
Then, I had to decide how to patch them together.
That done, I then had to balance their volume.
Once I did that, then I could sing to it.
The SHHHHH!! part was an inspiration, and reminds me of the Manger Sketch from Mister Bean.
