With 175 million users, Pandora launches revamped iPhone app; Android next

Pandora (s P) plans to launch a new version of its iPhone (s AAPL) app Monday afternoon, adding song lyrics, social features and more contextual information about the music on its streaming service to the app. The launch of an Android (s GOOG) app with the same features will follow soon after. The company also announced that it now has 175 million registered users, and Pandora CTO Tom Conrad told me during a recent interview that it had to walk a fine line to add all that functionality to the small screen without scaring off its massive user base. “It’s really important to us to stay true to the essential simplicity of Pandora,” he told me.

At the same time, Pandora wanted to bring a lot of the music discovery features that have been available for users of its web client to the mobile experience as well. This includes millions of pages with information about artists, albums and songs as well as the service’s 400 genre stations. Also new to the mobile apps are social features like an activity feed and user profiles.

User profiles within Pandora’s new iPhone app.

But how do you add all of that to a screen that’s four inches or less? Conrad’s answer: By building additional layers that are only visible to those who really want to know. He said it was tempting to put every new feature on top of the UI — but that would have complicated the core Pandora experience. A sizable percentage of Pandora’s mobile listeners will never use any of the features the company rolled out this week, Conrad told me, adding: “We are okay with that.”

Conrad, whose views on mobile design are also featured in our RoadMap book that attendees of next week’s RoadMap conference in San Francisco are going to get, told me that Pandora has gone full circle on user experience design: The service started with a very minimalist approach on the web in 2005, which it brought to the iPhone in 2008. For its launch on the iPad in April of 2010, it started to add additional features, which influenced the relaunch of the Pandora web experience last year.

Now that it has brought a lot of the web features back to mobile, the company is looking to once again revamp its iPad experience, with a full-featured Android tablet app coming soon after. The company also just announced a new app for Windows 8 as well as a cooperation with Microsoft (s MSFT) that will bring free and ad-free listening to Windows 8 mobile devices. All of this underscores how important mobile devices are to Pandora. “Over half of our audience listens on mobile,” Conrad told me.

Check out Conrad’s fireside chat at last year’s RoadMap conference below: