Given Milwaukee’s hot and humid weather, Florida native JJ Grey must have felt right at home kicking off his tour in a crowded Shank Hall Friday.

As easy as Grey’s music is to take in, it is difficult to pin down. It’s not retro but it’s not modern, either. Much like their Stax/Muscle Shoals forefathers, Mofro lays down a thick groove blending Hammond organ, Fender Rhodes piano, horns and harmonica. And like Otis Redding, Grey is a master of tension and release, building a song and stretching it out until it is all but snapped and then doubling back for more frenzy.

It helps to have songs as strong as set opener “Country Ghetto,” where the audience sung along on cue as the eight-piece band waded into the evening’s wall of swamp. Grey was certainly preaching to the converted, playing for an audience of aging hipsters and bra-less jam band chicks enjoying an in-door preview of festival season, but his testifying and Baptist wailing worked the crowd into a particularly excited frenzy, giving the show the energy of a frat-house kegger.

Grey’s strength is storytelling, and his songs are ripe with regional references to fireflies, cornbread and orange blossoms. His tangible details and the charged band create an authentic Southern vibe. The organ sounds like the keys are stuck with molasses, while the two-piece horn section punch, swell and wail as Grey’s wah-wah pedal gets a well-greased bluesy workout. Yet the key to the band may well be drummer Anthony Cole, who uses a stripped-down kit (no rack or floor toms) as he varies the rhythms to create space for the other seven players.

There are those who would have you believe that there is no place left for this kind of real music, a funky hybrid of rock ’n’ soul, but any band that can pack a club during Milwaukee’s all-too-short summer is evidence otherwise. At one point Grey noted this was really the first full gig this lineup had played together. Let’s hope they make it back to town when they reach their full potential.