Aziz Sahmaoui is a virtuoso of the stringed instrument known as the gimbri — the main sound of the North African trance music known as gnawa. He’s also pretty darn good at playing the ngoni, a lute instrument. And he's a former member of the late keyboardist and Weather Report founder Joe Zawinul's Zawinul Syndicate. Sahmaoui grew up in Marrakech and when he was seven hebegan learning the gnawa tradition from his father. He relocated to France in the late 1980s, and in 1995 was a founding member of the Paris-based Orchestre National De Barbes, a pan-Maghrebi ensemble of expatriate Berber and Arab musicians. Aziz now has his own band, University of Gnawa, which mixes everything he’s learned from both his father and Zawinul. They played yesterday at Millennium Park and they’ve got another show Wednesday at the Old Town School of Folk Music at 8:30 p.m.