Because the iPhone has a smaller storage capacity than fifth-generation iPods and many people’s iTunes libraries, you may not want to sync all your music to the phone. In order to control what music is synced to the iPhone, click the Music tab.
Here you can choose to sync no music, all music, or just selected playlists.
Music syncing does not happen automatically the first time you connect the iPhone to iTunes. As such, you have to specify what you want to sync and then resync before music is downloaded.
When you have made your changes, click the “Apply” button in the bottom-right corner.
