no one has a right to songs, but it is usual courtesy in singarounds and sessions not to perform something from someone else's repertoire. However if you don't know that a person sings it, or you're singing a different version, that's probably excusable. This courtesy also seems to have existed between traditional singers - singers had their "own" songs which no one else would perform.

Moot points worthy of further discussion, or even a separate thread, though I suspect it's already been gone over a hundred times! Some singers are more jealous than others - I've been spat at on various occasions for unwittingly covering the same ground, whilst others are just happy to know the song has a life beyond their repertoir. Some will claim their version to more correct than others, as in an unfortunate episode at an old folk club where two otherwise dignified and erudite ladies almost came to blows because one insisted her version of The Trees They Do Grow High was the proper one. That's one Child Ballad you won't find in Child, but the variants are legion and worthy of celebration, as is the case with traditional songs in general. I recently had a session with a notable Mudcat Ballad Singer and found that the ballad she sang (Childe Roland) had imprinted itself indelibly on my memory. Naturally I made it part of my repertoire, but should ever our paths cross in a singaround I'd most certainly ask her if she minded me doing it. I've worked in various duos with singers over the years and feel that the songs we did together belong to both of us, even if I served mainly as accompanist. I've lost count of the songs I've acquired this way, though many I've had to re-source on account of changes made by the singer.

How often have I worked up a song only to have it sung by another singer in the same session? All the more galling if they've got the words on their knee. Ultimately, the more people there are singing this stuff the better, and the deeper we dig in our sourcing so the less it should be a problem, so there's a lesson to us all really.