However you spin it, The Infamous Stringdusters are a bluegrass band at heart, although their sixth album, Ladies & Gentlemen, takes some sonic liberties. The 12 tracks also feature an all-star lineup of female musicians, including Joan Osborne, Lee Ann Womack and Sarah Jarosz, and save for some harmonies, their voices are the only ones you’ll hear. So, is it still a Stringdusters album? Despite the quintet’s instrumental signature, not everyone will agree. Some tunes easily fit the band’s classic sound, such as “Ladders in the Sky,” with bluegrass vocalist Claire Lynch, “See How Far You’ve Come,” featuring Sara Watkins, and Aoife O’Donovan’s “Run To Heaven.”In some instances—“Coming Back to You,” with Mary Chapin Carpenter’s deep croon, or the lighthearted “Rock and Roll,” with Abigail Washburn’s old-timey stylings—the legends make the song. Elsewhere, Jennifer Hartswick adds some tasty trumpet to the instrumental “Hazosphere,” and Joss Stone shines a light on the band’s rarely seen soulful side during “Have A Little Faith.” The only downside to such an ambitious assemblage may be the limits of replicating it live, though Nicki Bluhm (“Still The One”) and Della Mae’s Celia Woodsmith (“Old Whiskey Bottle”) have agreed to join the band on tour.