Warning: Apple’s new feature in its GarageBand app for the iPad may be habit-forming, creating a persistent and chronic time-suck that could swallow you whole.

It’s called Jam Session, and allows up to four people to “play” their iPads — or iPhones and iPod touches — together over Wi-Fi or Bluetooth and record songs.

When Apple’s marketing chief Phil Schiller unveiled the updated GarageBand app at the launch of the third-generation iPad in March, he introduced Jam Session in one of those we’re-all-kids-at-heart moments that Apple orchestrates so well. He even called Jam Session “the best new feature” of the incredibly popular GarageBand suite.

For $4.99, it’s downloadably yours. Musician or wannabe, it doesn’t matter. With a bit of practice, Jam Session can make a recording star out of anybody. It’s not perfect, and its smorgasbord of technical widgets can overwhelm. But it’s still awesome, precisely because of that rich mother lode of audio possibilities.

You can record up to eight tracks on an endless menu of both simulated instruments and orchestral synthesizers, tweak the sound effects to your heart’s content, then edit each track by cutting, looping or splitting them until you’re practically channeling famed record producer Berry Gordy.

To test-drive Jam Session, we reached out to the venerable J.C. Smith, a San Jose, Calif.-based blues guitarist and iPad newbie. For two hours one recent afternoon at Gradie and Jeannine O’Neal’s Tiki Studios, a 45-year-old recording shrine tucked into an East San Jose residential neighborhood, Smith and four members of his namesake band dipped into Jam Session for the first time.

“I’m not a computer guy, I’m a piano guy,” joked keyboardist Todd Reid, hunched over one of four iPads propped on the piano bench in front of him. While drummer Donnie Green started tapping on the drum set splayed across his glowing screen, his brother Robert began plucking the virtual bass.

Hovering nearby, tenor saxophone player Abraham Vasquez looked on with amusement. Jam Session doesn’t yet have a horn section, but Vasquez was able to dub in his instrument once the bluesmen had done their virtual business.

After running to the Apple Store earlier in the day to familiarize himself with this strange new app, Smith was ready to go. Jam Session requires a “bandleader” to controls things on one of the iPads, so Smith pushed a musical-note icon that “invited” the other three to join the jam. He then selected the “Hard Rock” guitar from an assortment of styles on the pull-down menu, added some fuzz distortion using a “Vintage Drive” special-effects tool, then went to town picking out a riff for a 12-bar blues number.

The others joined in. There were timing issues as the four tried to synchronize their sounds, so they tried laying down one track at a time, including Reid, who added a bluesy organ to the mix. In the end, they decided to go back to playing the four parts simultaneously. And then they nailed it.

It took time, patience and a fair amount of musical intuition. But 90 minutes into the session, after laying down then ripping up tracks to start over several times, the band had pieced together the backbone of what they’d eventually call “Eastside Shuffle.”

“Let’s add the sax now,” Smith said to Vasquez, who attached headphones to the master iPad, then added his blues solo right over the rhythm section, blowing the horn into the iPad’s built-in microphone. At one point, for reasons nobody could quite figure out, the finished song suddenly vanished from the bandleader’s iPad screen. But because the individual tracks were still on each of the tablets, the band was able to quickly stitch it all back together again.

“I think it’s a lot of fun,” Smith said after the session. “The iPad and the app enhance your creativity and give you new ways to think about your music and your instrument.

“I think it’s cool,” he said. “If I had an iPad, I’d play with Jam Session all the time.”