You get a strange crowd at a free concert. And, if the 5-year-old with a mohawk yelling “Go Zappa!” was any indication, you get the strangest crowd at a free Zappa Plays Zappa concert. Strange in a good way, though, as was shown at Thursday at the Square.

The young, up-and-coming London Souls opened the show, and their huge sound (not to mention hair) grabbed the attention of Lafayette Square almost immediately. Only seconds into their first song, people donning Frank Zappa and Zappa Plays Zappa T-shirts were nodding their heads to the funky-ish rock coming from Tash Neal on guitar, Kiyoshi Matsuyama on bass and Chris St. Hilaire on drums (all on vocals).

REVIEW

WHO: Zappa Plays Zappa with the London Souls

WHEN: Thursday night

WHERE: Lafayette Square

After they finished, Zappa Plays Zappa walked across the stage to an explosion of cheers. When Dweezil, the late and legendary Frank Zappa’s son, asked the crowd if they remembered the band’s “half-show” from last summer — it was canceled partway through due to lightning — the screams were deafening. And, as luck would have it, almost as soon as Dweezil commented that the weather seemed to be fine this year, rain started to fall.

But umbrellas opened up, and rain jackets appeared. As long as the rain stayed relatively tame, which it did, the band and the audience were not to be deterred.

Led by the calmly smiling Dweezil Zappa (on guitar and the occasional vocals), Scheila Gonzalez (sax, flute, keyboards and vocals), Pete Griffin (bass), Billy Hulting (various percussion), Jamie Kime (guitar), Joe Travers (drums and vocals) and Ben Thomas (lead vocals), the group never once stopped dancing and gesturing for the audience to join in as they performed some of Frank Zappa’s best-loved songs. They were here to have a good time, and it showed.

Freshly minted lead singer Ben Thomas showed off his vocal chops in an energetic performance of “Carolina Hard-Core Ecstasy” — his strong voice contrasted with his outfit, a white T-shirt, baseball cap and jeans — followed by “Montana.”

The songs themselves, though, weren’t the stars of the show. What Zappa Plays Zappa is famous for is its highly skilled instrumentation, and it was on full display Thursday night.

Watching and listening to Gonzalez on sax was enough to make anyone’s jaw drop, and even the crowd’s abundant air-guitarists couldn’t come close to keeping up with the lightning speed of Zappa’s playing.

That said, the concert wasn’t perfect. That so many showed up for the atmosphere and not the music meant that away from the stage, the chatter of conversation became so loud that it was difficult to hear the intricacies of the music.

Good thing that Zappa Plays Zappa’s musical virtuosity is the kind that you can see, even when you can’t hear.