Yes: Every Little Thing
Some strains of psychedelia where turning into prog rock in 1969, and Yes' self-titled debut shows a band pointing towards prog. Their take on the Beatles' "Every Little Thing" follows the mold of Vanilla Fudge and the early Deep Purple, who both created such elaborate arrangements of other people's songs they were almost new songs. But where both of those bands had a tendency to slow down faster songs, Yes come out firing on all cylinders. It's a tour de force that was probably a calling card for the band in their early days.
Over the top? Yes. But you have to admit, it has an energy that matches the lyrics much better then the comparatively tame original.