Hi Rose, I think the tape was given to Claire as a gesture of love, Claire perhaps not knowing that much about that era of music (or Joni Mitchell) but says to Sarah that it's such a beautiful song. I think the tape was labeled "Sarah's Tape" so it was probably a compilation of songs of the times Sarah had made, and Joni was there. To see Claire's mother singing along to the tape alone in the kitchen was just too great.
The show has consistently been terrific, but this one was the best. I think you folks on the west coast may still be able to catch this episode tonight. It's a cool show huh, Rose? Best, Gary