listenRealNetworks is preparing to roll out a new app and service called “Listen” that will let iOS and Android users set up and manage ringback tones — music clips and other snippets that play over the phone line, replacing the ringing sound for callers.

Ringback tones are used by millions of people on standard cell phones, but with Listen, the Seattle-based company is hoping to make them popular on smartphones.

Does the name ring a bell? It traces its roots to Listen.com, the startup that was acquired by RealNetworks in 2003, bringing with it the Rhapsody music service that has since been spun off by the company. When searching for a name for the new ringback service, RealNetworks’ mobile entertainment team found the Listen.com domain in the company’s portfolio and decided to use it.

RealNetworks’ new Listen app — for iPhone, Android and mobile web — will launch in the U.K. later this month and in the U.S. and other countries next year. The company will offer free and paid versions of the app, with pricing not yet announced.

listenListen builds on RealNetworks’ experience delivering ringback tones for standard cell phones, working in conjunction with wireless carriers. RealNetworks’ history with ringback tones goes back to 2002, when WiderThan launched what’s believed to have been the world’s first ringback tone service with South Korea’s SK Telekom. (RealNetworks acquired WiderThan in 2006.)

In contrast with standard ringtones, ringback tones have struggled to catch on in the U.S., but RealNetworks still manages more than 18 million ringback tone subscribers worldwide, and recently acquired London-based ringback tone company Muzicall.

RealNetworks says it values the overall ringback tone market at $4 billion annually.

“We think it’s a big opportunity,” said Max Pellegrini, president of RealNetworks’ Mobile Entertainment division, during a recent demo of the app at the company’s Seattle headquarters.

In addition to letting users assign ringback tones for different callers, the Listen app will serve as a light contact manager, showing top callers and letting users add images specific contacts.

The app can also be quickly set to give an audible status message to callers as they ring. For example, when Listen users are in a meeting, they can set the app to tell callers they’re unavailable and will call back later, before the call goes to voice mail.

This is part of RealNetworks’ broader effort to revive itself under the leadership of founder Rob Glaser, who has returned as the company’s interim CEO. Listen is the second major product launch for the company in recent weeks, following the debut of the new RealPlayer Cloud video sharing service. RealNetworks is still in the red, but in one sign of progress, the company recently said it expects to return to revenue growth in 2014.

In a news release announcing the Listen app and service, Glaser cited the size of the market overall, and RealNetworks’ early work (via WiderThan) to develop ringback technology on standard cell phones. “But until now, nobody has really reinvented or re-imagined what ringback tones can be in the era of smartphones,” he said.

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