You have seen at least a snippet of it, haven't you? Sometime during the past month, you've flicked on your television, zapped past your local pledge-hungry PBS station-and then switched back, in the channel-surfing equivalent of a double take. Mesmerized, you watched a pianist in a big-shouldered, boy-blue suit, backed by an orchestra, playing windswept, rousing orchestral pop, like variations on the thirtysomething theme song. After it's over, you may have even gravitated, a little glassy-eyed, to the nearest record store to buy the album of the event-which would explain why John Tesh's Live at Red Rocks (GTS) has leapt up dozens of spots on the Billboard pop album chart in a matter of weeks. Yes, that John Tesh, the gangly, square-jawed cohost of Entertainment Tonight. You have a right to laugh, but in New Age and contemporary-jazz circles, Tesh is serious business. At this moment, three of his 12 (!) albums are on the New Age chart, with the No. 2-ranked Live at Red Rocks nipping at the heels of the current chart-topper, Yanni's Live at the Acropolis. Like that double-platinum multimedia event, Tesh's album is a lush, symphonic concert album taped in a gorgeous physical setting; the long-form video features enough shots of the burnished Rocky Mountains that the orchestra should be renamed the National Geographic Symphony. Tesh, however, is not content to ape Yanni, in whose band he once played. The proof is in the video. Near the beginning, a slew of children surf a massive flag above the heads of the crowd, which easily tops Bono and his one measly banner at U2's 1983 Red Rocks concert. During the next hour and 50 minutes, dancers and gymnasts (including a resurrected Nadia Comaneci) contort themselves during songs, and volcanic explosions erupt on either side of the stage. Unlike the sullen alterna-rockers who take to the stage looking like they're awaiting root canal surgery, this man knows the value of showmanship. One reason the whole production is so hypnotic is that you keep watching to see what over-the-top gimmick Tesh and his producers will come up with next. Just as the stage production verges on surreal overkill, so does the music. The multiplatinum sales of Kenny G have shown there is a large audience that wants to chill out to easy-listening instrumental pop with a sorta-hip, sleek- jazz edge. Tesh has clearly studied this genre well. In fact, when saxophonist Everette Harp steps out front on Red Rocks, the ensemble sounds like a G tribute band. At other times, thanks to the wildly huffing and puffing Colorado Symphony Orchestra, the music has the sweeping, rushing drive of a soundtrack score: ''A Thousand Summers,'' for instance, would be ideal accompaniment to a Western's cattle drive. All of which is easy game for critical target practice. Yet Live at Red Rocks is as fascinating a phenomenon as exists-compared with, say, the current state of the increasingly predictable Lollapalooza tours. In a sense, it represents the ultimate taming of the rock spirit. On Red Rocks (as on past albums like Sax on the Beach), Tesh covers songs by Phil Collins and Sting, each of which slips easily into a jazz-fusion holster. Tesh's own songs have the ultraclean guitar licks and drums of a rock session band. Halfway through Red Rocks, it even rains, just like at Woodstock-although, instead of chanting ''no rain!,'' Tesh stands awkwardly on stage with an umbrella and asks a stagehand, ''Should we wait or should we go?'' We are living in more cautious times, after all-or maybe he's much hipper than we thought and is making a veiled reference to the Clash song. Well, probably not, but consider this. Much more so than movie stars-or entertainment-show hosts-can ever do, pop stars embody their audience's fantasies. Seated behind his grand piano, dapper in his three-piece suit, Tesh looks like a financial planner at your bank. And that image is probably a large part of his appeal. Pumping his fist in the air as the orchestra hits a crescendo, grinning like a grateful kid when the audience cheers, and running out to the crowd to plant a big wet one on his wife, Connie Sellecca, he epitomizes the boomer generation's fantasy of being a rock star for a night. ''I don't know if you folks know it,'' he says at one point, ''but each and every one of you are, at this moment, sitting right smack-dab in the middle of my biggest dream-being here, doing this. Yeah!'' Given that he financed the stage production himself, released the album and video through his own company, and is a modest, unspectacular pianist, Tesh is also a product of the anyone-can-make-music, do-it-yourself spirit of underground rock. Never mind Green Day and Rancid-John Tesh is a punk! Live at Red Rocks could almost be an infomercial-a seminar on how to be all that you can be with a lot of money and a lot of faith. It's the post-Elvis version of the American dream, available on compact disc and long-form video at the mall nearest you. Averaging out the C+ music and the A- spectacle, I am compelled to give it a B.