Well, we may be defining 'attributable' differently

And/or perhaps "directly". If I've learned a tune from person a who learned it from person b, I might use indirectly.

And of course people do pick up songs and tunes at clubs and sessions - but you often don't have to go very far back to find someone who DID get if from the Bothy band, or Steeleye, or whoever - and you can tell that by the style of the performance, with the influences clearly on view to the ear.

OK so I can go to the sessions I go to, not knowing who is going to be there on the night or how the music is going sound or feel, what the tunes on the night will be, being aware that how an individual tune may go depends on who starts it as might the choice of tune that follows it...

To pick on one instrument, I might be aware that the guitarist on the evening might be a DADGAD player, std tuning player or one that changes tunings and all individually very capable of adding their own individual sound to the general feel of the night.

And in all this some clearly defined "stamp" is going to be heard?

Sorry Tom. It's reading like the prs line to me.