Thanks to Carl, who started it with his fantastic post on The Swell Season in concert. He mentioned the duet performed a Pixies song, and I (the Pixies fan) - just had to know which Pixies song. Mary saved the day by revealing it was "Cactus". Ahhhhh. Thank you, Mary. :)
Here's the YouTube video, link courtesy of Carl, of the Swell Season performing "Cactus" - from the Pixies album I alway remember as "The One with the Flamenco Dancer with the Bare Boobies."
I smiled at Glen Hansard's little shout-out to Kim Deal (bassist and back-up vocals for The Pixies), who was apparently there with The Breeders.
Glen Hansard: "This is a Pixies song. In honor of Kim. I hope she's here. I hope she's listening."
They are a great pair. I ended up buying the "Once" soundtrack this afternoon. I am glad to say I enjoy it tremendously.
Big thanks to Carl and Serene for recommending great music that I must have!