Many prog fans and sites say this is the ultimate prog song. That's what I don't know, but for sure you'll find here all the basic elements of classic prog and many more. First of all, the intricate musical plot, including tempo changes, instrument dialogues, syncopated rythms, complex vocal arrangements, mystic and ecological lyrics and -last but not least - mountains of technical prowess! Is this all? No, that would make a good song, a display of skills, not a masterpiece as undoubtedly it is.
The 7'' version of "Roundabout" peaked #13 in USA single charts.
IMHO the extra value is provided here by two important qualities: harmony and balance. All the instruments play as one, both technically and emotionally. A perfect clockwork, yes, but with a beating heart inside. A last note: a single version of this song exists, during 3'27'' and released in january 1972, but please if you don't know Roundabout (well, there must be some...), listen to the full album version (8'29''): you'd loose 5 minutes of pure joy.