You make ashes for them. Wood to start with, but then anything you might have left of them, anything that was theirs. It is not a necessary part, the possession, but if you have it, then it is done. The song is an old one, about how mankind was scattered after the fall of the Tower of Babel — it's not difficult to teach.

[She'd learned it quickly, after all. It's a haunting melody, yet an oddly beautiful one. It sings of the stars and the moon, the trees and flowers, the lakes and rivers. Mankind, scattered across the world, and the yearning to come home again.]

There is a place in the song for the Speaker's name. You...you are singing it to them, you see. Calling them back to you, and guiding their memory to the ashes you have made for them. So that when they are scattered again, it is not from being lost. The ritual finds them, so that there are remains to be treated properly.