Yes' third album, The Yes Album, was probably their universally accepted peak. For once, I am in alignment with the general listening public. This album included the classic rock radio favorite "Seen All Good People" as well as the much better, but slightly less renowned "Yours is No Disgrace".
The kings of prog would go on to release dozens of studio and live albums after The Yes Album, much of it very good(Owner of a Lonely Heart, notwithstanding).
Getting back to The Yes Album, here is a much lesser known track called Starship Trooper. I love how this song transitions from a very proggy start to a melodic, soulful piece by the end. Starship Trooper was co-written by founding member and bassist Chris Squire, who left this Earth too soon the other day at the age of 67.
https://www.youtube.com/watch?v=DKftiJS30Cs