Some of these I knew; I'm looking forward to exploring the ones I didn't.

My favorite prog bands (from the Canterbury school) rarely covered someone else (though they have been covered by diverse artists including Whitney Houston and Weyes Blood). On their "Girls Who Grow Plump in the Night," Caravan incorporated "Backwards" a Soft Machine tune (both bands evolved from the early psychedelic group Wilde Flowers) into their suite "L'auberge du sanglier." I bring this up because for me, "Backwards" is the most beautiful tune ever written.

Here's a live (somewhat later--several significant personnel changes) Caravan version of "Backwards" followed by "A Hunting We Shall Go," which opened and concluded the original Caravan Suite); this gives you a good sense of the melody itself: https://youtu.be/6DcZu9WIbWs

Here's the Soft Machine original (it was itself a section of the album side-length composition "Slightly All the Time"): https://youtu.be/A667xEMQQWg

Here's the Caravan original suite which contains "Backwards" and three other segments; this is texturally the most complex statement of "Backwards"; it's orchestrated, features David Sinclair on piano and synthesizer, and is flat-out gorgeous--starts at 4:27, ends at 9:14: https://youtu.be/6zbVfNJKpuM