When you’re listening to music online, you can painstakingly create your own playlists. You can rely on technology such as that employed by Pandora to choose songs you’re likely to enjoy. Or you can drop into Songza, where the hard work of constructing playlists is done by the site’s music experts; the only technology they use is their own good taste. The Music Concierge feature lets you choose a scenario (such as “Cooking Breakfast” or “Unwinding After a Long Day”) and helps you home in on a genre (like “Smooth Rockabilly” or “Frat-Rap House Party”). Then you just sit back and listen.