The Burial song is a fan favourite from Xena Warrior Princess and it was sung by Xena at the funeral pyre of friends in a few episodes. Lucy sang a snippet of the song at the 2013 Xena Convention and a fan uploaded the video to youtube. Normally I don't post Creation Xena Convention videos (because filming is not allowed) but this is a snippet of the song and not the full thing. Below this video is the full song.

Burial was written by Lucy Lawless and Joseph LoDuca

 

2013 Xena Convention

 

 

The full Version as sung by Lucy Lawless on Xena Warrior Princess

 

 

Q: Does Lucy Lawless,star of Xena, Warrior Princess, sing the haunting song heard on the show from time to time?-Merry Crow,Cordove, Teen

A: Not only does Lawless 32 sing that melody-known as "The Burial Song"because it's used whenever an Amazon dies-she created it. The New Zealand born beauty told us the tune came to her while jogging one day, and it was orchestrated by Joseph LoDuca, who won an Emmy for the show's score. "We never dub Lucy's voice," notes LoDuca, who also wrote a Xena score based on Wagner's Ring Cycle, which has been featured this month. Incidentally, Lawless will hang up her shield in May; Xena is being cancelled after six seasons.
http://www.ausxip.com/articles15/parade_magazine.htm