Before the rise of smartphones and tablets, it was hard to imagine Internet audio content ever supplanting radio. The limited Web programming that was available may have been convenient to listen to at one's desk, but it didn't do much good in the car, on a jog or otherwise on the go.

Today, traditional radio is still far from being displaced, but streaming audio from mobile devices sure does offer an attractive, personalized and more interactive alternative. For some of the strongest examples, look no further than NPR's digital efforts. The historically radio-centric news organization has wasted no time building a bridge to the future with its digital products, including a few rather impressive mobile applications.

Most recently, NPR has expanded its music-focused iPhone app to the tablet screen. NPR Music for iPad, which went live yesterday, takes their voluminous archive of music coverage and live performances and packs them all into one very well-designed app.

The content is broken down in a few different ways, which makes it easy to browse depending on what users are looking for. It can be viewed by content type (articles, videos, etc) or by genre or individual radio programs. There's also a search utility if you're looking for a particular artist. If the band or musician you're looking for has appeared on any NPR program in recent years, they'll come up in search results. This could be an interview on WXPN, video of a live "Tiny Desk Concert" performance, a feature on "All Things Considered" or just about any other kind of music coverage NPR does.

The interface is fluid and intuitive, with blocks of content sliding and falling into place when you make a new selection on the navigation. When you pull down and release to reveal additional content, the page blurs quickly blurs in and out of focus, which is a nice touch. They could have simply sized the iPhone app up and made it fit on the iPad without any bells and whistles, but they didn't. It's evident that the team put some thought into the user experience on this one.

If the app has a single feature that makes it worth downloading, it's probably the playlist builder. As you come across audio clips and shows you want to hear, whether it be via search or by browsing, you can add queue them to play one after another. This ends up working like a sort of personalized radio station, not of songs, but of NPR's best in-depth music coverage.