In the Immigrant Song by Led Zeppelin....during Chorus when Page plays A-E-A chords...he is getting a tremolo type effect on the chords....How is he doing this....I have tried a Volume Pedal, Toggle Switch On-Off, Guitar Volume Switch Roll....but none of it sounds right. If anyone has played this song and knows what effect or technique Page is using to get this sound...your advice will be most appreciated. Thanks in advance