Does anyone know how Animal Collective makes that sound in "For Reverend Green"? It's the sound that starts the song off and plays throughout the whole song.

Here's the link for those of you who haven't heard the song.

It's a good song too.
Its my favourite Animal Collective song =D

And that noise, I believe, is an overdriven guitar with a tremolo effect. That said, they're very electronic so it could be a keyboard or almost anything.