Hubert Sumlin may not be the best-known guitar player in the world, but he's certainly got his fans -- guys named Jeff Beck, Keith Richards, Jimi Hendrix ("he's my favorite guitar player") and Eric Clapton, who put together the fabled "London Howlin' Wolf Sessions" as an excuse to play with Sumlin. "Clapton, Richards, they were all honored to play with him," says Pat Day.

Day, a harp player with a local blues band, the Rhythm Masters, will bring Sumlin to the Psyche Delly tonight, a fan's gesture that recalls similar support-your-inspiration concerts by the Nighthawks in the early '70s. Day, who has been helping to book the Legendary Blues Band (Muddy Waters' old backups) and James Cotton, got involved when he inadvertently found out how little money Sumlin was making. "I was flabbergasted. The Rhythm Masters make more than him, and he helped write American music! I thought I'd help the guy."

Helping Sumlin, who suffered a mild heart attack in Austin several months ago, is something blues players seem to enjoy doing. Stevie Ray Vaughan, the fiery Texas guitarist who performs at Constitution Hall on Thursday, has given Sumlin a few of his favorite guitars ("that's the least I could do for the guy") and a lot of credit. Asked about a particular way of playing with his right hand, Vaughan told Guitar Player magazine he'd either use a pick or his finger, or "I'll Hubert it."

Sumlin, one of 13 children in a Mississippi delta farm family, was already playing in regional juke joints at age 12. He first started working with blues harpist Howlin' Wolf (a k a Chester Burnett) in the early '50s and together they helped define the electrically amplified blues style that's been such an influence on rock 'n' roll. "Anybody in rock 'n' roll knows him because of the Wolf," says Day. "He has a certain style that's so much his own."

Sumlin will be backed by his regular band, West Side Express, and the show will feature another fine guitarist, Bob Margolin, for many years a Muddy Waters mainstay.