The Good: Songza offers playlists that are perfect for just about any activity or mood you're in. It's free to download, and there are no commercials. The Bad: The app lags a bit if you try to browse through categories while listening. There are no links to supplementary artist or track information. The Bottom Line: Songza offers one of the more unusual (and most enjoyable) streaming-radio experiences we've tried. Songza is an increasingly popular streaming-music app that offers a different take on the type of programmed radio experience that Pandora initially made popular. Rather than generate playlists based on specific songs or artists, this app tries to offer up the right selection of tunes for specific activities you might be engaged in. Whether you're looking for mellow tracks to help you unwind on your commute home or high-octane drumbeats for powerlifting at the gym, Songza should have the playlist for you.While other streaming-radio apps typically start you off with a search bar, Songza starts with its unique Concierge screen. Here, it presents you with six choices of different activities you might be engaged in. Six may not sound like very many, but worry not because these six actually change depending on the current day and time. As an example, here on a Friday afternoon, Songza asked me if I wanted music for Driving, Working, Epic Walking, and so on. I chose Epic Walking, which led to another menu of choices designed to help the app home in on exactly the right playlist for my stroll. Songza wanted to know if I was, perhaps, "Walking Away from Explosions" or "Rockin' Leather Pants." Naturally, my answer was neither because I was simply "Swaggin' Down the Block." Once the app ingested my answer, it presented me with its suggested playlists, of which I selected "St. Ides Sippin'," a mix of '90s-era East Coast rap tunes that evoke images of Brooklyn stoops and 40-ounce bottles of beer. Needless to say, this was the perfect playlist for my midday break.