POP REVIEWS : ACTS AND REVELATIONS OF GENESIS

Fans arriving at the Forum on Monday for the opening of Genesis’ five-night stand already had their tickets in hand--the shows sold out instantly months ago--but they had other consumer options to consider, some symbolic in one way or another.

In the lobby, the $35 sweat shirts (surely an all-time concert concession price record) were doing brisk business. Doing less well outside was at least one older man--whose concept of Genesis obviously dated back to the veteran band’s more, uh, “cosmic” days--was approaching concert-goers hawking any number of psychedelics.

The younger, upscale crowd--whose concept of the band has likely been formed more through Phil Collins’ recent pop solo hits--appeared to be paying the vendor no mind. Many were probably too young to even recognize the names of the man’s out-of-fashion wares. Outdated drugs, no way; outrageously overpriced tour merchandise, si .

There you have in a nutshell the rock ‘n’ roll generation gap that Genesis has tried to bridge -- with mixed results. Seven years into the decade, this once-great ‘70s band still suffers from an ‘80s identity problem--albeit with no commercial fallout.

The old and new shades of Genesis were all on display in generous portions during Monday’s 2 1/2-hour show--the “progressive” Genesis, the pure pop Genesis, and various permutations in-between.

And while the group (which has been down to a trio for about eight years, with two permanent sidemen for tours) has proved more than adept at cranking out the Top 40 hits, it was the more musically adventurous material that ironically provided both the high and low points of the Forum gig.

Toward the end of the show, “Supper’s Ready” and “Los Endos” were happily anachronistic curios for the faithful, throwbacks to the days when the band sought to stretch the constrictions of orthodox rock music.

But you won’t find pieces remotely like those on any of the group’s recent albums. The latest LP, “Invisible Touch,” does feature a few numbers that recall the expansive sound of old, but these are the weakest cuts on the record; the kinds of songs that were once the highlights are now the dead meat. These guys only seem to have their hearts in the most basic and simple material nowadays--it’s as if they’re too pooped to do anything but pop.

The latest album’s low point, “The Brazilian,” also provided the concert’s optimum nap time. The cheesy instrumental--which comes off like a bad parody of what Genesis used to do best--featured some surprisingly cheesy synthesizer tones from Tony Banks, who usually knows better.

But the bulk of the set, of course, balanced between the trio’s ‘80s hits (highlighted by some especially fetching guitar work from Mike Rutherford on “Abacab”) and almost the entirety of the latest album.

While the modern singles are a marked retreat from the ambition of old, they are usually redeemed at least in part by the kind of interesting musical textures that are absent from, for example, Collins’ latest solo record. Though some of the more disillusioned old fans might disagree, there’s still plenty of room for Genesis to get wimpier.

Needless to add, the infamous overhead light show was niftily state-of-the-art, even without psychedelics.