how to multi task on iPhone sdk?

I want to be able to multitask in Matt Gallagher's AudioStream iphone application which can be found over here http://cocoawithlove.com/2008开发者_JAVA百科/09/streaming-and-playing-live-mp3-stream.html I tried uibackground by adding to info.plist but it isn't working any ideas on how to make it work? I did read the apple documentation but I have failed to find anything. any code would be appritated

thanks,

add this to your info.plist

<key>UIBackgroundModes</key>
    <array>
        <string>audio</string>
        <string>voip</string>
        <string>location</string>
    </array>