Yes during their early stages tonight. I think most people, when they think of Yes, think of all the highly produced, highly conceptual material they recorded in the period from around The Yes Album onwards. That really was when the band took off and that's pretty much their trademark era.
But there was a slightly earlier incarnation, from their beginnings up to their second album, Time And A Word from which tonights track, the Richie Havens penned No Opportunity Necessary, No Experience Needed opens the album. Even here, you start to get an idea of the direction they would eventually head into. But it would take a personnel change (Tony Kaye on keyboards and Peter Banks being replaced by Rick Wakeman and Steve Howe) in order to affect that new direction.
If you're familiar with this track it may sound a little different to you. This is actually the original mix and not the one that appeared on the finished album. You can hear Peter Banks guitar work more clearly here where it's almost completely mixed out in the released version and it makes for a different impression of the song.
In either case, here is Yes as they were pretty close to the beginning.