Bonnie Raitt is well known for handpicking and generously showcasing her tour mates. But she couldn’t have been more accommodating at Wolf Trap on Sunday night, when she shared the stage with bluesman Taj Mahal, her friend of 40-plus years and her “favorite artist ever.”

After an opening set in which Mahal’s Phantom Blues Band exuberantly kicked off “The BonTaj Roulet” revue, complete with brass, reeds and evocative set design, Raitt significantly overhauled her show. She engaged in cozy duets and launched a long series of encores that further capitalized on the horn-powered double bill, culminating in a festive mix of newly arranged hits and blues, boogie, soul, reggae and calypso treats.

Of course, being in good company is one thing, being in good voice another. Raitt was in terrific voice, and she knew it. She belted out “Something to Talk About” and other up-tempo tunes in husky, lusty tones, and charged two signature ballads — “Angel From Montgomery” and “I Can’t Make You Love Me” — with as much as power as poignancy. Even so, her singing didn’t overshadow her expert (and extensive) bottleneck guitar work, with its customary bite and resonance.

Fronting a tight band that prominently featured a new recruit — veteran keyboardist and singer Ricky Peterson — Raitt joked at one point that her voice keeps getting lower, which is undoubtedly the case. But it’s as soulful as ever, perhaps even more so, and the chance to perform alongside Mahal, who had no trouble reinvigorating his hits (or mimicking Howlin’ Wolf’s deep roadhouse moan), was all the inspiration she needed.