You could say that Sara Watkins’ solo debut has been a lifetime in the making. The 27-year-old singer-songwriter and fiddle player spent nearly two decades’all of her teenage and young adult life’as one-third of Nickel Creek, the Grammy Award’winning acoustic trio that used contemporary bluegrass as a starting point for its no-genre-barred sound. Along the way, she’s hinted at her desire to do a project of her own and even organized some exploratory sessions in Los Angeles about six years ago. Now, with Nickel Creek on indefinite hiatus, she is releasing her self-titled solo disc, recorded in Los Angeles and Nashville and produced by former Led Zeppelin bassist John Paul Jones. It features an impressively wide range of backing players and old friends, including itinerant alt-country duo Gillian Welch and Dave Rawling, Tom Petty and the Heartbreakers keyboardist Benmont Tench, Elvis Costello drummer Pete Thomas; fellow travelers from the bluegrass world like Tim O’Brien, Chris Eldridge, Ronnie McCoury and Rayna Gellert; and her Nickel Creek bandmates.