The Arthurians, from a very early time in their history, have sung songs, usually from sources that come from, or claim to come from, folk tradition. No-one quite knows why, other than that people obviously seem to enjoy singing them.
A particular favourite is Matty Groves, which has been described in the Society's magazine, Ceridwen's Cauldron, as "a composite of a degenerate American version" of a folk song preserved in Child's collection of ballads, originally entitled Little Musgrave and Lady Darnell. The version that the Society sings is very similar to that sung by Fairport Convention on their album Liege and Lief.
The Society songbook was first produced by Stewart Grime when he was President of the Society in 1990, to help new members learn the songs more quickly at events such as the Michaelmas Bonfire and Storytelling and the Mediaeval Banquet. It was revived in an expanded form by Louise Dennis two years later, who has written on Arthurian Society songs herself.
The first three editions were simple photocopied sheets, but in 1994 Andrew Jackson and Elspeth Edward produced a fourth version, with a card cover, available for sale to members at the price of one pound, but with several kept in reserve for general use. This version not only had the texts of songs, one or two of which were much argued over, but music as well to aid anyone who happened to bring an instrument along.
The songbook includes several songs but only one of them has a direct reference to Arthur, which you can read for yourself here; but the Oxford Arthurian Society anthem par excellence has to be Matty Groves!