Round About Midnight or Sketches of Spain?

You shall wear the bottoms of your trousers rolled.

http://www.openculture.com/2017/03/listen-to-grace-slicks-hair-raising-vocals-in-the-isolated-track-for-white-rabbit-1967.html

Drenched in echo, Slick sings with martial precision, completely in command of her vibrato and dipping and rising all through the Phrygian scale (also known as the Spanish or Gypsy scale.) And no wonder, the song was written in 1965 after an LSD trip at her Marin county home where Slick had listened to Miles Davis’ Sketches of Spain over and over again for 24 hours.

Grateful Dead Spanish Jam also seems to be a direct lift. Think it was the Valentine's Day 68 set that had me really notice that.