"Jimi is neither a great songwriter nor an extraordinary vocalist," wrote Jon Landau in a 1967 Rolling Stone review of "Are You Experienced." "The poor quality of (some of the) songs, and the inanity of the lyrics, too often get in the way" of the musicianship.

A year later, reviewing "Axis: Bold as Love" in the same magazine, Jim Miller echoed Landau. "Jimi Hendrix may be the Charlie Mingus of rock. ... But his songs too often are basically a bore," he wrote.

And even while a leader in the late '60s rock scene, he didn't always fit in. He was an African-American in an increasingly white musical landscape, a man who'd leapt from the chitlin' circuit -- the R&B clubs where he'd backed Slim Harpo, the Isley Brothers and Little Richard -- to headlining theaters where the Airplane and Traffic played. (And just before that, the Experience famously hit America by opening for the Monkees on a handful of 1967 tour dates.)

"To succeed with white audiences he had to achieve a balance," Cross writes in "Room Full of Mirrors." "Too much 'show' and he'd lose them. ... At the same time, Jimi needed a select few of those moves to establish himself as a showman because just being a talented guitar player -- black or white -- was not a ticket to stardom."

Today, in an era even more determined to put its musicians into distinct little marketing-approved boxes, a crossover artist such as Hendrix -- a black rock guitarist -- is even rarer. Gary Clark Jr., an African-American guitarist who's been compared to Hendrix, is filed under "blues," and has observed that he's aware he's going against a commercial grain that practically demands African-American musicians play hip-hop or jazz, and white musicians play blues or rock.

"For a black male, the sound of the blues is pre-civil rights. It's oppression," he told Vanity Fair. "In high school I had a friend who asked me why I played the blues, that black people don't play blues."

There have been attempts to crack those stereotypes, but if anything, it's even harder than it was in Hendrix's day, a time when AM Top 40 had plenty of variety, free-form FM radio welcomed experimenting and record labels strained to catch up with it all.

"I grew up listening to all the classic rock and being completely taken by two people the most -- Jimi Hendrix and Janis Joplin," says Sophia Ramos, 43, a member of the Black Rock Coalition, an organization co-founded by Living Colour guitarist Vernon Reid to foster the growth of black rock musicians. Until recently, Ramos focused on the rock world, whether fronting rock bands or singing backup on rock records.

She's faced the marketing problems first hand. In the '90s, she led a rock band called Sophia's Toy, whose debut record went unreleased by its label because, she was told, "there was no market for female rock 'n' roll singers." Even today, she blames the industry more than the fans for not being open to black rock musicians.

"That's the crazy thing that (affects) we people of color who do rock 'n' roll -- or who do any music that's not what we're supposed to be doing -- it's the industry. It's not the audience," she says.. "When it comes to the coveted spots of who are we going to push in the star machine, those that have the money and the means to do so rarely are going to look at a black artist and say, 'Yeah, I'm going to get behind that.' "

Ramos' new project is a show of ranchera and bolero music.

"I've put rock 'n' roll behind me," she says.

'He broke a lot of barriers'

Could Hendrix have broken out of such classifications these days? Kramer says he believes he could have. To borrow Duke Ellington's phrase, he was "beyond category."

"When I think of Hendrix, I put him in the pantheon of Charlie Parker, Miles Davis, John Coltrane, Louis Armstrong -- he really is in that league because his individuality was so strong and his message was so strong and his mastery of his instrument was so complete," he says. "He was a maverick. He broke a lot of barriers, musically and in every way."

But Covach wonders if the audience would have followed. Would people fill arenas and stadiums to hear a 70-year-old Hendrix play lengthy jazz solos? Would his albums still go platinum?

"What would probably have happened to Hendrix is he would have released a whole series of records and critics would say they're fantastic and he'd have his fans on the Internet -- but then he'd go out and do shows and do 'Purple Haze' and 'Foxy Lady,' " he says.

Different times.

But if there's a notable sign that Hendrix isn't ready for the classic-rock bin -- that "People, Hell and Angels" isn't just for baby boomers reliving Woodstock -- it's in the fans. Covach observes his students are fascinated by the guitarist, and biographer Cross says his 13-year-old son is a convert.

"There forever is a new crop of young guitar players (listening)," he says. "He's a rite of passage for any guitar player."

What they learn is that Hendrix isn't just about guitar pyrotechnics. Yes, he probably would have stood out in the YouTube age, thanks to his showmanship. But the reason his music continues to thrive is beyond that image of the guitar hero. It's the space between the notes.

"For me, it's always a thrill," Kramer says. "I go into the studio and pull up a tape, and Jimi's talking to me -- at the end of a take, he's saying, 'Hey, how about that take?' And I go, 'Yeah, yeah, yeah. Try it again.' But it always puts the hair on the back of your head up."