from the very nice GQ article on Billy Strings:

"In early August, Strings found himself with a rare week off.

He was going to be in Western Michigan rather than at home in Nashville, so he could be closer to Ally’s family as they awaited their son’s birth. There were bassinets to build, cradles to construct. He remembered that Phish were coming to Van Andel Arena, a relatively small room in Grand Rapids, for two nights for the first time since 1998. He sent Anastasio a text: “You think you could float me a couple guest spots?”

Anastasio misread Strings’ request for the guest list as an ask to sit in. “Let’s dooo it!” Anastasio responded immediately, and then: “Talking to the guys right now! Excited!” When, a month later, I told Anastasio about his mistake, he laughed a long time. “He didn’t think he was going to play with us?” says Anastasio, pulling up his text thread with “Billy Strings Real.” “I thought he meant come in for a guest spot.”

The morning of that first show, Anastasio dispatched a list of 16 potential songs for the next two nights, so Strings worked doggedly to learn them all until the moment he walked onstage. By the time he began playing, his left hand was already aching from all that solo rehearsal. He knew he was joining one of the tightest jam bands in history, with 40 years of experience; with that old self-doubt creeping in, he didn’t want to flub it.

“I didn’t want to piss Phish fans off, you know? I didn’t want to go out there and play a big wrong chord, which I probably did several,” he says, chuckling. “But at least I practiced.”