Auerbach recently started having "picking parties" at his home in Nashville's West End neighborhood. One guest was McCoury, 78. A veteran of Bill Monroe's Blue Grass Boys, he is one of the last living links to bluegrass's golden era. "He flies Bill Monroe's flag hard," Auerbach says. "I was raised on the Stanley Brothers. I didn't know that you can't be in both camps – bluegrass beef, man." Those parties pushed Auerbach to start writing on acoustic guitar. "It couldn't be a fragment supported by studio magic," he says. "I wanted to be able to sit down and just play 'em and have them work. I've never been able to do that."