Bruce Hornsby fans who have attended his shows may not find it all that odd that the keyboardist has abandoned his 88s for dulcimer on his first studio album with his longtime backing band in six years. Still, for most listeners this will come as a surprise, especially since there is zero piano on this 10-track set. It’s yet another side of a restless, artistically driven musician who delights in expanding his musical genres from bluegrass to jazz, blues, gospel, pop and rock along with a high-profile side stint handling piano duties for the Grateful Dead. 　　 　　Not surprisingly, this is a more unplugged, rootsy, but not entirely stripped down or acoustic offering that’s a coherent and refreshingly offbeat broadening of Hornsby’s talents. His subtle, dry sense of humor is in full flower for the folksy “Tipping,” (“I must admit I’d rather get service for a song”) that finds the singer wondering what the correct amount of gratuity should be above a peppy mix of jazzy organ and Garcia-ish electric guitar courtesy of Gibb Droll. The humorous lyrical touch extends to the Celtic strains of “TSA Man” about exactly what its title suggests and the frustrations we all experience going through airport security. 　　 　　Hornsby revisits his own “The Valley Road,” originally from 1988’s Scenes from the Southside, opening up its sonic vision by extending the tune to almost seven minutes, taking it into far more rustic, backwoods Appalachia territory. In either version, it’s a terrific song and performance. 　　 　　Since the dulcimer isn’t much of a lead instrument, it provides a rootsy backdrop to tightly knit songs. That’s particularly true of the closing churchy “Celestial Railroad” which greatly benefits from guest Mavis Staples whose testifying vocals bring some of the Band’s “The Weight” vibe to the tune. Droll’s Garcia-like snaking guitar accompaniment is a bonus. 　　 　　The set is focused more on songwriting than technical proficiency, attributed in part to, as Hornsby says in the press notes, the instrument’s limited chordal palette, which keeps the writing simple and direct. Still, both Hornsby and his band are in fine synch throughout, bringing a loose, comfortable homey feel to the material. 　　 　　It may be just a brief excursion in Bruce Hornsby’s ever growing and eclectic catalog, but the charming, completely unaffected Rehab Reunion feels like a natural, even logical road to take on a lifelong musical journey that has seldom been predictable.