Found a great app in the itunes store that allows you to get the pitch shifting sounds that Jimmy Page gets while Robert Plant has one of his orgasms. Its worth getting if you ever want to play along to the song otherwise that section is long and boring with very little guitar in it. Anyway hope it helps as a demo of the app. My playing wasn't the best but you should get the idea with the app. 
Old Guitar Dad
Never too old to learn
Never too old to rock
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