Mandolinist Rich DelGrosso, Guitarist Mary Flower and multi-instrumentalist Martin Grosswendt have earned steady streams of praise for their outstanding string skills. Combined, these three have earned nine Blues Music Award nominations and enjoyed rave press reviews and top festival slots all over the world. And they do strum, pick and bow up a storm on their debut album together as the Ragpicker String Band — but it’s their tight trio harmonies that especially dazzle. The acoustic dream team summons the spirits of everyone from the Mississippi Sheiks and Blind Boy Fuller to Jim Kweskin and R. Crumb as their voices and fingers fly through the mists back to the golden prewar age of folk-blues.

Classics by the likes of the Mississippi Sheiks, Sleepy John Estes and Blind Willie Johnson — combined with new originals by Flower and DelGrosso — allow this virtuosically fearsome threesome to leaven their serious instrumental and vocal chops with social satire and mischievous humor. Just as Kweskin and Crumb filtered the songs and sounds of their prewar folk-blues heroes through their own modern sensibilities and considerable personalities, so do the Ragpicker String Band. Jump from a fabulously fretted, sublimely sung trip to the past like Trimmed and Burning to a laughing lament of modern times like Google Blues and you’ll find out what an uncommonly fine stew of traditional and contemporary ingredients they’ve cooked up. They even season it with a delectable dose of jazz via a conspicuously piano-less romp through Thelonious Monk’s standard Blue Monk.

Mark Hoffman, the co-author of Moanin’ at Midnight: The Life and Times of Howlin’ Wolf, called DelGrosso’s mandolin mastery “the best since Yank,” and Yank Rachell devotees everywhere agree. Add what Mary — a two-time finalist at the National Fingerpicking Guitar Championship — and Martin (“One of the best fingerpickers I ever heard play” —David Bromberg) bring to the table and you know you’re in for a string exhibition of the highest order. Add to that their irresistible harmonies and irrepressible humor and you’ve got a “side project” worthy of the front-and-center spotlight.