Singing a song that is not on the list!
Listed in Recording Help & Tips.
Reply by werewoofGOLD 
You can't...
However, you can certainly find many backing tracks on sites like youtube, and download a free recording program onto your computer, then record them on your computer...
Post by Tash27GOLD
I would love to be able to sing a couple songs that I cant find on the lists and record them but I dont know if I can do that here. If someone could let me know if we can or not and if we can how that would be great! Thank you!