So a 'session' is a gathering of unpaid musicians, preferably drawn from the local community, where singers are the exception? Is that what is measnt by 'real' in this context?

For me, a session promoted as a Comhaltas session has a particular meaning- depends on your view of that organization, of course- the majority of small towns & even villages in Ireland would have such a session.

Traditional music is a form of social interaction, and if you're not communicating with the people, especially in a public bar, that is pointless. and you're doing the music a disservice.

So the idea of a circle of musicians (even of a high standard) sitting in a circle playing to each other surely defeats the object, and unless it's done in the privacy of your own home, this approach can do nothing positive for the music. It's certainly not 'real' in my book!