CAMBRIDGE, Mass. (AP) _ Luther ''Guitar Jr.'' Johnson and Son Seals stood off to the side, sipping drinks while another guitar slinger cut through a nasty solo - mouthing the notes and stomping his feet to keep time, eyes closed.

Being veteran bluesmen, the two are tough to impress. But that night they rolled their eyes and shrugged in mock resignation. Johnson kept time by bobbing his head back and forth; Seals did more of a slow roundhouse roll.

Everyone was smiling; a new sheriff was in town.

About an hour later, though, when Seals and Johnson were jamming, the young hotshot who had christened the House of Blues stage already was gone.

Little Mikey, after all, is only 13, and his parents don't want him out too late.

''I'd really like to do this professionally. It's what I love to do,'' Mike Welch said later. ''I haven't made a career decision, though. I want to see if I can grow as a player. And finish school. And go to college.''

Little Mikey is the future of the blues, a distinctly American music with a distinguished past stretching from Alabama's cotton fields to Chicago's bars.

Southern black culture after the Civil War created the blues, and the music eventually split into two factions: country blues, a man singing about his life and playing guitar or harmonica; and urban blues, which usually featured a female singer and horns.

But while those in the industry say the blues is enjoying its biggest revival yet, not everyone is tuned in.

''White folks are the ones spending money on it,'' said Paul Averwater, president of the Beale Street Blues Society in Memphis.

Many say young blacks aren't listening, and there are several theories - unlike jazz or rap, there's no room for musical exploration in blues' 12 bars; your parents listened to it, so it's not cool; it's a reminder of segregation and poverty, with undercurrents of oppression.

''Blues is something associated with our older generation,'' said Bobbie Banks-Reid, 22, an administrator at the Blues Foundation in Memphis. ''It isn't something we have gone through . .. it's not something that we can readily relate to.''

Jerry Washington - ''Old Wash,'' to his listeners in the Washington, D.C. area - has been the host of a three-hour blues Saturday program on WPFW for 16 years. He spins records by Bobby Blue Bland, Muddy Waters, B.B. King, Robert Cray, everyone.

''White people support the blues. Without them you wouldn't have a large audience for your concerts and your shows,'' Washington, 63, said from his home in Silver Spring, Md.

Banks-Reid said, ''We do try to make things as inexpensive as we can to allow it to be patronized by people of all colors.''

According to legend, the devil met Robert Johnson at The Crossroads and taught him to play his guitar as though he had four hands. In exchange for his soul. Johnson, recognized as the King of the Delta Blues, died at age 26 under suspicious circumstances, amid whispers of Satan collecting his due.

More likely, Johnson learned his craft from Blind Lemon Jefferson, Charlie Patton, Son House and others who sang, played guitar and wrote heartfelt, pointed songs about life in the Mississippi Delta.

Now, when the Rolling Stones bring John Lee Hooker on stage, or Eric Clapton cops an Elmore James slide guitar riff, or U2 cuts a song with B.B. King, they're not just singing; they're repaying a debt.

''Blues is the tap root of all popular music today,'' said Isaac Tigrett, the hirsute hipster who founded the Hard Rock Cafe chain and hopes a sprinkling of Houses of Blues nationwide, and eventually worldwide, will be as successful.

According to the Blues Foundation, a nonprofit organization dedicated to preserving and perpetuating ''America's original indigenous musical art form,'' the numbers are up:

Record labels devoted to the blues have increased 26 percent since 1990; blues clubs have proliferated by 52 percent in two years; the number of societies and organizations dedicated to the music is up 39 percent; the number of new artists, blues festivals, attendance at small and large venues, blues publications, memorabilia sales, all increasing.

Tigrett's House of Blues is ambitious. The blues shrine includes two bars, a performance stage, the Take It Easy Baby blues accessories shop and a restaurant serving juke joint and international fare, including a not-very- roadhouse-like ''veggie burger.''

Some of the floorboards were adapted from Muddy Waters' boyhood home, and the cathedral ceiling features 56 plaster-relief pictures of blues legends, at a cost of $1,500 each. The CD player holds 600 blues discs, and monitors hooked up to computer software scroll histories of the artists.

Dan Aykroyd, Paul Shaffer and Joe Walsh officially launched the club. Investors include Aykroyd, John Candy, River Phoenix and John Belushi's widow, Judy.

Tigrett's plans include House of Blues Media Inc., which will produce radio and television shows, including a syndicated ''Live 3/8 From the House of Blues'' hosted by Aykroyd.

Tigrett, who bailed out of the Hard Rock Cafe chain in 1987, also intends to open other clubs in New Orleans, Chicago and Los Angeles in the next two years.

The House of Blues borrows its motto from Jake and Elwood, the Blues Brothers: ''We're on a mission from God.''

''Our whole thing is to perpetuate the culture,'' Tigrett said.