Buy on the fly.
Browse New Releases, What’s Hot, and Genres. Take a look at Top Songs and Top Albums. Or find exactly what you’re looking for with a quick search. Play a 30-second preview of any song, then tap once to buy it. Your music starts downloading instantly, and you can keep tabs on its progress by tapping the Downloads button.

Sync it back.
When you connect iPhone to your computer, the music you bought on the go syncs to your iTunes library. If you’ve only partially downloaded a song to iPhone, your computer completes the download automatically.