found this bit on J playing with Mark Mulcahey…
liepaper.com
H: J Mascis of Dinosaur Jr. and Joey Santiago of The Pixies appear on the new record. Have you been friends with both of them for a long time?
MM: J lives around where I live, Massachusetts, and I played a gig with him in London when he was playing as J Mascis + The Fog. We had a good time playing that gig. They do this thing up here every year called Transperformance, where a lot of the bands from Northhampton pick a theme and everybody imitiates a band. A couple of years ago it was southern bands, so me, him, and three or four other guys did The
Allman Brothers. We had never played together, but we had a great time.
I said to him, "Dude, I’m making a record if you want to play on it." He’s like, [Mark proceeds to do a funny J Mascis impersonation] "Yeah, you know I’m around," or some vague answer. It was just real organic. He came in and played for the day. You know, he’s great.