Wilhelm was an important member of two San Francisco Bay Area groups, in two different decades. In the 1960s, he was a guitarist and songwriter for the Charlatans, often identified as one of the very first San Francisco psychedelic groups, although they were more appropriately described as mixers of blues, folk, jugband, and nineteenth century saloon music. In the late 1970s, he joined the Flamin' Groovies on guitar for a while. There is also some solo material by Wilhelm in which he comes across as a hippie Old West cowboy of sorts, just as he looks in those old Charlatans photos. His low scaly voice delivers tunes that wander across the blues, vaudeville, and folk landscape with some rock thrown in on his Michael Wilhelm album.