I remember working this out probably 30 years ago, and I'm very much in agreement with Lee Mitchell. Double dropped-D is the tuning - the dischordant chord pretty much fixes it, as you have the Eb on the B string against the open D which would otherwise be an E string. Apart from the "If the Gipsy cannot dance" section, which is a little busier, it's quite an easy number to pick up.

It shares quite a lot structurally, I think, with "Another Rain" from the same album - that one is in straight dropped-D I seem to remember.