My memory seem to be nagging at me that Buchan was actually following Lord in his 'Singer of Tales' analysis of The Oddessy. Some interesting newevidenced slants the argument in Folk Song: Tradition, Revival, and Re-creation.(ed. Russell & Atkinson ~ Elphinstone Institute, Aberdeen University, 2004).

I would suggest that 'written' variations are just that - variations - not improvisations although they may have started out that way. The Northumbrian pipes do have thier own tradition of 'variations' of course.

My own opinion is also that variation in accompaniment, although it may be improvised or accidental (or both!), is still accompaniment and a different beast to true improvisation of the (critical) melodic line which, among the 'trad' performers I've known, has always been linear and not chordally based.

I once asked Packie Byrne about variation and improvisation during a whistle workshop he was running in the beachstore @ Sidmouth in about 1968 - only to discover that he couldn't play a scale without decorating it! Creation and recreation is constant.

All that probably doesn't help

Tom