Yes

Origin
Arguably, Yes can be considered the most progressive rock band of this era. The band was formed in 1968 by bassist Chris Squire and vocalist Jon Anderson. They were accompanied at that time by guitarist Peter Banks and keyboardist Tony Kaye along with drummer Bill Bruford. Later, Banks was replaced by guitarist Steve Howe and Kaye by keyboardist Rick Wakemen. Bruford would eventually be replaced by drummer Alan White. The band's peak album sales and concert draw were with the Anderson, Squire, Howe, Wakeman lineup with either Bruford or White on drums.

Influences
Different members of the band brought different influences. Anderson was clearly influenced by a variety of singers and he was a fan of Simon and Garfunkel with obvious similarities between his own vocal capabilities and Art Garfunkel's. Squire progressed as a bass player from early rockabilly to more jazz-based influences and Bruford brought a lot of jazz influence, himself. Howe and Wakemen were heavily influenced by classical styles.

Main Creative Force
Chris Squire was probably the most influential writer of Yes first albums and continued to be the likely guiding force, but the band could never really separate itself form the unique vocal styles of Jon Anderson. Deciding which of those two were the true creative heart of the band is difficult. And even then, on the most definitive Yes releases of the 70s - 'Close to the Edge' and 'Fragile', the obvious influences of Wakemen and Howe on the sound are undeniable. If I had to give the nod to any one member of the band, it would probably be Chris Squire.

Most Likely To Be A Mainstream Rocker
Bill Bruford, the drummer for Yes' first three records, has to be the most likely suspect here. Like most jazz-influenced musicians in rock and roll, he is probably the most flexible and indeed, he played with a vast array of musicians over the years.

First Hint of Prog Brilliance
The third album was called 'The Yes Album' and brought Steve Howe into the band. It was clearly the signature of how progressive this band would become. Songs like 'Yours Is No Disgrace', 'Starship Troopers', and 'I've Seen All Good People' would be performed by the band for the rest of their career and the sophisticated interplay of bass, vocals, guitar, and keyboards were unique.

Prog Pinnacle

The prog pinnacle for Yes was really two albums - 'Fragile' and 'Close to the Edge' but in many ways, Fragile is the definition of that peak. It is the first Yes album to feature Rick Wakeman on keyboards and the first to feature their iconic cover art by Roger Dean. The album also features five pieces generally regarded a solo efforts for the band's members. 'Cans and Brahms' is a Wakeman rearrangement of Brahms. 'We Have Heaven' is a vocal symphonic piece by Anderson. 'Five Per Cent for Nothing' is mostly percussive in nature and was written by Bill Bruford. 'The Fish' is a Chris Squire composition that is largely bass guitar. 'Mood For a Day' is a classical guitar solo piece by Steve Howe. In the world of prog excess, this album is outstanding.

While 'Close to the Edge' doesn't feature the solo ego excess tracks of 'Fragile', it does consist of three lengthy pieces: 'Close to the Edge' which covered side one and ran eighteen minutes plus; 'And You and I' which was ten minutes long, and finally 'Siberian Khatru' which was nearly nine minutes. Whereas 'Fragile' boasted a radio hit in 'Roundabout' which saw a lot of airplay in the burgeoning AOR format, 'Close to the Edge' was virtually unusable by radio except as an emergency time filler for DJ's with digestive ailments.

Influenced By Them
Yes had a direct influence on some new wave artists of the eighties who were heavily synthesizer-vocal based, among them the Buggles and Cinema. They were also a precursor to the prog supergroup, Asia, which featured Yes guitarist, Steve Howe. It's easy to see some influence of Yes on the more symphonic prog predecessors of the eighties and nineties.

Legacy
Yes has had a fractious and confusing legacy. The band has split and reuinted in multiple incarnations. Wakeman was in and out of the lineup, depending on how he viewed the quality of the material being written by Squire and Anderson. Howe and White were also in and out over the years. Dispute over the ownership of the Yes name led to a group performing under the name 'Anderson, Bruford, Wakeman, and Howe'; essentially four-fifths of Yes not allowed to call itself Yes. At one point there were basically two versions of Yes which actually got together to record an album called 'Union' in 1991. The album included all the members of the classic lineup along with Trevor Rabin who has sung with the band off and on and Tony Levin on bass for much of the ABWH tracks. The album won Yes a Grammy for the song 'Masquerade' and also produced one of their best mainstream hits with 'Lift Me Up'. There was even a tour with all eight members of the two bands. Yes continues to exist in some form or another but it is difficult to define which members are or are not with them. And no, they are not in the RRHOF. They have sold an estimated 13.5 million albums in the US and likely even more in Europe.

My Personal Take
I loved Yes. At the same time, they are close to being seen as the epitome of prog excess. Their live album, 'Yessongs' was three LPs and included parts of Stravinsky's 'Firebird' and bits and pieces of Wakeman's prog solo album, 'The Six Wives of Henry VIII'. The movie version of 'Yessongs' is a fairly spectacular capture of the band performing live, but elements of it are eerily prescient of the 1984 mocumentary, 'This is Spinal Tap.' Honestly, in many ways it was the epitome of self-indulgence to record albums, go on tour, make a live concert album, and then make a documantary film about the live tour. The only saving grace for Yes is that theirs was actually less self-indulgent than Led Zeppelin's 'The Song Remains the Same'. In any case, to this day, it is hard to find any live rock performances that feature five musicians so perfectly at the top of their game as Yes in the Yessongs era.