SAN FRANCISCO >> Steve Jobs re-emerged from his latest medical leave Monday to show off Apple Inc.’s latest innovations and sustain the hope that he eventually will return to dream up more ways to reshape technology.

The highlight, as usual, came at the end of Jobs’ presentation. He was onstage for less than 30 minutes during a nearly two-hour event that primarily featured his subordinates.

Ever the showman, the Apple CEO announced that the company had struck licensing agreements with all the major recording labels on a new music synching system.

It will allow people to put all the songs they have ever bought from the company’s iTunes store on up to 10 devices at no additional charge. Apple is offering to do the same thing with all books and applications previously purchased through its online stores. 

All future iTunes purchases also will be automatically sent to all the devices, too. None of the transfers will require devices to be plugged into a single computer. It will automatically happen over wireless connections.

“Keeping all those devices in sync is driving us crazy,” Jobs said.

Jobs’ keynote address at a conference for application developers marked his first onstage appearance since he unveiled the second version of Apple’s tablet computer, the iPad, three months ago.

It comes five months after Jobs went on his third medical leave of absence in the past seven years to deal with an unspecified medical issue. He has previously survived pancreatic cancer and undergone a liver transplant.

Unlike during a six-month leave in 2009, Jobs, 56, hasn’t said when he is coming back to work. The uncertainty makes his every appearance even more of a spectacle because people don’t know if it will be the last time they will see one of the world’s most influential CEOs and cultural taste-makers.

Looking as frail as he did in his last appearance in March, Jobs didn’t discuss his health Monday. 

That wasn’t unusual; he has consistently treated his health as a personal matter and insisted that Apple’s board remain mum, too, much to the frustration of some shareholders who believe they deserve to know more about the condition of the man whose vision drives a company with a $312 billion market value. That’s about $300 billion more than when Jobs, Apple’s co-founder, became the company’s CEO in 1997.

Apple, though, tried to strike an optimistic note by playing the James Brown song “I Feel Good” as a prelude to Jobs’ appearance. When the song concluded, Jobs stepped onstage to a standing ovation and a “We love you” shout from one man in the audience. Jobs smiled and said the warm reception “helps.”

After his presentation, Jobs talked briefly with Connor Ellison, a 13-year-old boy he met earlier this year at a group that supports organ donations. When Ellison asked Jobs how he was feeling, the Apple CEO said “I feel good” and posed for a picture. Afterward, Ellison said he and Jobs share the same doctor. Ellison also said Jobs had invited him to come down from his home in Folsom, Calif., to attend the event in San Francisco — about a two-hour drive.

While he was onstage, Jobs seemed animated as he gestured frequently and paced about the stage. He appeared to walk up the steps of the stage slowly after sitting down in the audience a couple of times while other Apple executives demonstrated features of the iCloud service.

“He delivered all the key points, but it doesn’t look like he is getting any better,” said veteran Silicon Valley technology analyst Rob Enderle.

Jobs didn’t look much different from his March appearance for the iPad 2, said Tim Bajarin, president of Creative Strategies and a longtime Apple watcher. Bajarin downplayed Jobs’ limited time on stage on Monday, saying he “almost always” relies on underlings to handle the bulk of demos at developers’ conferences.

Having Jobs appear at major events remains important to preserving Apple’s market value and keeping shareholders at bay, Enderle said. 

“As long as he is still showing up and looking like he can still do the job, that helps keep the pressure off the board to replace him,” Enderle said. 

Tim Cook, Apple’s chief operating officer, has been running the company, just as he has through all of Jobs’ medical leaves. Jobs still has a say in major decisions.

Apple shares fell $5.40 Monday to close at $338.04. Before Jobs’ appearance, the shares had been up slightly.

“I don’t think the stock reaction is about (Jobs’) health,” said Piper Jaffray analyst Gene Munster. “Almost every investor I talk to doesn’t believe he’ll be part of the company in a year or two.” 

The stock has declined 3 percent since Jobs announced his latest medical leave Jan. 17. During that time, the technology-driven Nasdaq composite index has fallen 2 percent.

The new synching service Jobs announced Monday could be a boon for consumers because more than 18 billion songs already have been bought through iTunes. Apple said Monday that more than 130 million digital copies of books have been downloaded from its store so far. The new feature to have additional copies of previously purchased songs and books sent to more devices is available now.

Jobs also unveiled a way for most people to keep their entire music collections on the company’s computers without going through the time-consuming hassle of uploading each song over the Internet.

The $25-per-year service, called iTunes Match, will allow people to play their personal jukeboxes on any device with iTunes software instead of keeping them tethered to a personal computer that must be synced with other devices. It’s aimed at people who have transferred their CD collections to the iTunes library on their own computers, but also gives music labels a chance to be paid for pirated music. Apple is paying most of the iTunes revenue to the labels.

The music streaming is part of broader service, called iCloud, that represents Apple’s attempt to persuade the tens of millions of people who own iPhones, iPads and iPod Touches to store documents, video and photos in three data centers, including a recently completed one in rural North Carolina that cost more than $500 million. 

The allure for consumers is to have all their digital content available on any device running Apple’s mobile software, called iOS.

For Apple, the iCloud service represents a response to similar storage services offered by Google Inc. and Amazon.com Inc. Although those rivals have a head start, Apple is betting it can make the concept of online storage more appealing and convenient. ICloud replaces a failed syncing service called MobileMe, which Jobs said “was not our finest hour.”

It will take a few more months to find out if Apple is taking the next step in the evolution of digital music and Internet storage. ITunes Match and most other iCloud features won’t be available until the fall when Apple plans to release iOS 5.

Apple announced it will release the next version of its operating system for Mac computers, called Lion, next month. A preview of that software, which will cost $29.99, was handled by two other Apple executives. Lion will give Apple a jump on Microsoft Corp., which recently said it won’t release the next version of its Windows operating system until next year.

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AP Technology Writer Barbara Ortutay in New York contributed to this report.