Instead, he's pulling more pearls from his leather-bound journal, lessons learned from 15 years on the road with the Roots, the Grammy-winning Philadelphia hip-hop band he left last year.

If his audience has come expecting tales of big money and wild parties, that's not on today's program. What Hub wants to get across is something less sexy:

"Drugs and disease are waiting for you outside that door," he tells the young musicians sitting at his feet - 26 rapt students at the Settlement Music School's Germantown branch. "You can't play your show from a hospital bed."

He tells them that learning to read music is important. That to be a successful musician, one must be reliable. That the occasional shower is a good thing. Professionalism.

"You can be the best guitar player or keyboard player in the world, but if the man paying the money doesn't like you, you're never going to work."

It's old-head, eat-your-vegetables stuff he's laying on the kids in Nirvana T-shirts, backward caps and ragged jeans, players from the city and suburbs who are spending two weeks in the Summer Jam program at Settlement, where Hubbard, now in his 40s, studied while growing up in West Philadelphia.

A course, not just a class

Thick as his sound, Hubbard is 6 feet tall and well-muscled in a sleeveless T-shirt from the Roots' 2004 Tipping Point tour of Japan. He talks fast and furiously, his stories suggesting that he and self-doubt are unacquainted.

Like how at Carnegie Mellon, where he studied upright bass, he told his orchestra conductor that he didn't need to practice. "I was rude, but I was right."

Or how, when the Roots were nominated for the 2000 Grammy for best performance by a rap group, he wrote a speech because he knew he'd be called to give one. Backstage, he said: "It's about time in contemporary black music that someone gets an award who can actually play an instrument."

So why would he quit a wildly popular group? The road. It's hard on the body and soul. He tired of the 60-hotels-in-two-months drills, performing after 40 minutes of sleep.

Once it was a novelty for a hip-hop band to feature live musicians. "Now," he says, it's 'Been there, done that.' " He says he needed to write and produce, get his own songs out there.

"People don't know the extent of my musical ability," he says. "If I don't put it out there now, what am I waiting for?"

City of stars

They need to learn the city's musical history - not just that jazz greats like John Coltrane lived here, but that people like Gamble and Huff worked here, producing so many hits.

"We're close to New York, but we have our own distinct vibe and sound."

Finally, it's time to play. He sets down his Fiji water and picks up his Fender jazz bass, its frets wearing smooth, the paint around the strap pin chipped from merciless banging on stage.

And he begins an astonishing solo. It's something he wrote a few years ago called "African Sunrise," gentle harmonics followed by propulsive slapping. He plays it loud, then soft, soothing, then raucous, straight, then synthesized, singing scat over the foundation.

Later I grab him and ask about the piece.

How would you describe what you played? I ask.

"Good," he answers and laughs.