iPod controls to your home screen!

Double tap the home button while the screen is locked to bring up your iPod controls, "Play", "Stop", "Next", "Previous" and the "Sound level control".
iPhone 4 isn’t just an amazing phone. It’s an amazing iPod, too — one that lets you listen to music, watch video, and browse everything with the touch of a finger. Flick to scroll through songs, artists, albums, and playlists. Flick through music by album artwork with Cover Flow. Shake iPhone to shuffle songs. Create playlists right on your iPhone. And don’t worry about missing a call. The music fades and pauses when iPhone rings, and a pinch of the center button on your headset answers the call.