Mozes, a mobile marketing company, on Tuesday launched a service at the New Music Seminar in Los Angeles that lets concertgoers buy merchandise during the event using their cellphones.

The Palo Alto, Calif., company is one of dozens of technology startups seeking to tap into live events as a source of marketing and digital commerce.

For musicians, selling merchandise is becoming an increasingly important revenue stream as sales of the music itself dwindle.

It's not just T-shirts and posters. Mozes has tested sales of seat upgrades, backstage passes and digital downloads via mobile phones during shows.

But posters work too. Taylor Swift, at a concert last summer in Foxborough, Mass., asked her audience to text in orders to reserve a $25 limited-edition poster that they could buy later.

Here's how it works. Fans are prompted to text a message and are sent a reply with a link to a website where they can make their purchases.

Mozes, founded in 2005, has long been helping marketers reach out to fans during live events with sponsored giveaways and contests. Fans text their e-mail addresses for a chance to win a prize, say a personal phone call from Lady Gaga, that is funded by the corporate sponsor.

About 10 million people have taken artists up on such offers via Mozes over the years, according to the company's chief executive, Dorrian Porter. At an Umphreys McGee concert last year, for example, the band asked the audience to text song requests, which appeared on a large screen to the left of the stage.

-- Alex Pham

Twitter: @AlexPham

Photo: Audience members at an Umphrey's McGee concert were invited to text song requests that would appear on the large screen to the left of the band. The band took their cues for what to play next from the audience's texts. Credit: Chad Smith Photography via Mozes.