Tom Petty - Learning to Fly

HAL9000

I very rarely use effects so apologies if this is something, that really, even my grandmother should know...

What is the effect on the rhythm guitar on this track that gives it a slight swirling kind of sound? I'm guessing it's some kind phasing or Univibe going on but it's reasonably subtle (to my untrained ears anyway). Can anybody enlighten me further please?

Thanks.

Alnico

Sounds like a subtle phaser to me.

EDIT: Possibly a double tracker.