In today’s musical environment, when an inability to play more than three chords, an exposed belly button and breast implants and a willingness to write songs about killing your own mother are all held as valuable commodities, I can’t express how refreshing it was to go to a concert featuring five performers who were extraordinarily good at (gasp!) playing their instruments — and who weren’t afraid to craft and perform epic songs that let them prove themselves again and again over the course of a chockablock evening of intense, passionate music.

I’m referring to Yes, of course, who appear to have severed their last tie to their simpler, more pop-flavored phase by jettisoning superfluous guitarist Billy Sherwood earlier this year, thereby returning to the classic five-piece concert set-up that defined their glory days in the ’70s. Most of the members from those glory days remain, though, with Jon Anderson (vocals), Chris Squire (bass), Steve Howe (guitar) and Alan White (drums) still in the fold, now supplemented by (relatively) young Russian keyboardist Igor Khoroshev.

It’s impossible to downplay the immensity of the shoes that Khoroshev has to fill as a member of this band, given the roles that legendary synthesists Rick Wakeman and Patrick Moraz (and to a lesser extent organist Tony Kaye) have played in the group’s evolution. Based on the evidence displayed Sunday night at SPAC, however, I don’t think anyone was complaining about his capabilities — and I’d even go so far as to argue that his energy, fresh approach to the group’s material and nifty extra touches on percussion and vocals have provided the sort of spark that Yes has been missing for much of the past twenty years.

But rest assured they’ve found it again: I don’t exaggerate when I say that Sunday’s two-hour, eight-song set may well have been the most audacious, riveting and instrumentally spectacular rock concert I’ve ever attended. The set list for Yes’ current “Masterworks Tour” was selected from songs chosen by fans through the group’s web site, resulting in a concert that featured such mammoth, audience-pleasing pieces as the 29-minute “Ritual (Nous Sommes Du Soleil),” “Gates of Delirium” (23 minutes) and “Close to the Edge” (20 minutes).

While the potential for boredom would seem high given such apparent compositional excess, I can state absolutely that the thrills rarely stopped during Yes’ performance, as one virtuoso performance followed another, leaving the audience literally gasping with pleasure throughout the show. Quibblers may no doubt sniff that this reaction was nothing was misplaced nostalgia, given that the most recent song in the evening’s set list was 26 years old, but I’d argue that interpretation, instead attributing the crowd’s reaction to wonder and amazement at watching Yes in fine form while Yes did what Yes do best: grinding through those monumental masterworks that no one else would dare to conceive, much less play.

Kansas’ opening set, on the other hand, worked best as nostalgia. The five-piece (missing guitarist-keyboardist Kerry Livgren, but otherwise with all the key players in place) played 45 minutes of crunchy new material and complex (if obscure) album tracks, generally satisfying, only occasionally veering too close to the Journey zone for comfort. But when Kansas closed their set with the triptych of “Point of Know Return,” “Dust in the Wind” and “Carry On My Wayward Son,” man oh man, was the house on fire with ’70s lust — and was it clear to all and sundry just why those songs have been radio staples for so many years. Damn good stuff played damn well.