If you Google "The downfall of Yes," you'll come across a YouTube video that some enterprising fan of the seminal progressive rock band concocted, using the now well-known footage from a film about Hitler in which der Fuhrer is having a meltdown, in German, at the expense of a few of his underlings. In this version, a YouTube auteur created subtitles in which the raving Hitler is now freaking out about lineup changes in Yes -- specifically, the departure of singer Jon Anderson and the addition of Benoit David to the band's ranks.

This is all in bad taste -- nothing about Hitler is funny. But it does raise an issue that, as "classic" bands continue touring well into their 60s, affects fans and potential fans of that band.

When is a band no longer a band, but simply a brand?

This summer, we'll see several major groups with half, or even less than half, of their original members on stage. The Guess Who, a perennial favorite on the Buffalo summer concert schedule, might well be called "the Guess Who It Isn't," since singer Burton Cummings and guitarist Randy Bachman are no longer in the house. Kiss will arrive at Darien Lake in September with only founders Gene Simmons and Paul Stanley on board, stand-ins Tommy Thayer and Eric Singer handling the musical figures pioneered by original members Ace Frehley and Peter Criss.

And then there's Yes.

When the band plays Artpark's Tuesday in the Park series this week, Jon Anderson will not be in attendance. Anderson's replacement, the aforementioned Benoit David, won't be singing for Yes, either. Third generation prog-rock outfit Glass Hammer vocalist Jon Davison will be manning the microphone, following David's as yet unexplained sudden departure. Which makes Davison a replacement for the replacement.

I've been conducting an informal poll all summer long, trying to take the temperature of the seemingly limitless flow of area prog-rock fans I encounter at shows, in clubs, or even while walking my dogs. I ask them if they'll go to the Yes show, considering all the seismic shifts in the lead singer department.

Three quarters of these folks immediately scoff, say "No way!" and proclaim their eternal allegiance to Anderson as "the only true voice of Yes music." (Anderson was rather unceremoniously ousted from Yes following a severe respiratory illness that prevented him from filling tour obligations a few years back. He has made it more than plain that he's none too pleased with this state of affairs.)

Most of the rest say they'll go, simply because the music remains vital and, frankly, awesome, no matter who is singing. Throw in the inviting Artpark setting, and the low-dough ticket price of $5 advance, $10 after Sunday, and the general feeling among this portion of the crowd is, "Why not?"

Yes has a history at Artpark, we should note. It was on this very site, on the stage of the indoor amphitheater, that the band played a historic concert -- with Anderson singing, and a symphony orchestra joining the band -- back in 2001. So Yes an awful lot to live up to on Tuesday.

I've been asked many times this summer if I plan to be at the Tuesday show and what my take on the whole Anderson/David/Davison mess is. Well... hell yeah, I'm going! Most definitely, I'd prefer Anderson to be in Yes, where he belongs. But founder/bassist Chris Squire, guitarist Steve Howe, drummer Alan White, and keyboardist Geoff Downes are all going to be on the Artpark stage. Squire and Howe in particular are, in my view, two of the finest rock musicians extant. White is no slouch, either, and Downes has a history with Yes, having played on the evergreen "Drama" album -- interestingly, during the brief time that Anderson split with the band for the first time, in the early 1980s.

How much of a substance can be whittled away without completely changing the character of that substance? It's tough to say. There are certainly bands that tour under their original banners with dubious lineups playing the classics, presumably before a percentage of audience members who are either oblivious to the changes, or simply don't care, as long as they hear "the hits." Observe the career of Journey: The band continues to pull in more than respectable numbers as a live act, even though singer Arnel Pineda is clearly attempting to clone departed singer Steve Perry's parts. Journey fans don't appear to be too broken up about any of this.

Progressive rock fans are a different breed, however. They don't appreciate being messed with, and they are not easy to fool. I'm hoping Yes will convince them of its collective sincerity on Tuesday. And then I'm hoping the band wraps up this tour and gives Jon Anderson a call.