[stcredzero]

Jazz musicians can also do this with chord charts, as long as someone knows the lead.

In one session I used to play in, there was a player who could play any Irish tune after listening to it just one time through, so long as someone else kept playing it.

There's an Irish flute player in the Bay Area who I love playing with and listening to. He's 100% variations all of the time, all the way through, but he does it right and everything fits.

Adding additional challenge is the minor variances in tunes that occur between regions and jam sessions.

TBH, many North American players just fluff those. Often, it falls to more capable players to match up to the others.