As part of my research into a potential book project, I've been looking up some medieval song references. One of them is the so-called 'Lyke-Wake Dirge', the first references to which date back to the 15th century. The word 'Lyke' is an primitive English version of the Dutch word 'lijk', meaning 'body'. The dirge was intended to be sung at a wake for a newly deceased person, in the presence of the body, as a sort of pre-funeral meditation for the mourners. It references what happens to the soul when it dies, and the consequences of having helped - or not helped - others during one's life. It was almost certainly a pagan song in its remotest origins, but had Christian elements incorporated into a later version; hence the references to purgatory and Christ.
I knew it from Pentangle's version, recorded in 1969. To my surprise, there are many others out there. A quick YouTube search reveals at least a dozen renditions (including a pagan version which may be closest to the song's original form). For those who don't know it, here's Pentangle's version, which is both musically the most attractive (IMHO) and the easiest to understand. If you'd like to follow the lyrics (and learn more about what they mean), I recommend this article. Open it in another tab or window and read along as you listen.
All in all, a very interesting piece of musical history.