It turned out (as I discovered from research the next morning) to be an NPR series that Michael Feinstein does, called Song Travels, where he features an specific performer and goes through their career, talking about it and having them play on record, in studio, and sometimes with Feinstein joining in.
What caught my ear was that this was an hour with Peter Yarrow and Noel Paul Stookey, of Peter, Paul and Mary. And it was very enjoyable and interesting. Yarrow's voice is no longer strong -- he's 75 at this point -- though he sings with great passion, which is half the battle with folk songs. Stookey, though, is still in great voice, and he's a year older.
I'd have posted this earlier, but initially the most I could find were 10-15 excerpts. I guess after a bit of time has passed, they post the whole thing. Here it is. I can't embed the show, but if you click here, a website will open with a music player, and the show will start automatically.