Television is running woefully low of paltry excuses to stage a celebration. Tonight at 8 on Channel 4, NBC offers "Dean Martin's Comedy Classics," an hour of taped clips from the old "Dean Martin Show" (1965-1974). They probably should have called it "Contractual Obligation," since it looks for all the world like something thrown together to satisfy a tattered old pact between the network and the star.

Orson Welles, hauling his hull around as a shill for NBC now, hosts the hour from a studio in Burbank and Martin, curiously, hovers silently in the background, like a night watchman or a well-dressed vagrant whom we see arriving at the studio in a $65,000 Ferrari. When Martin finally speaks, at the end of the show, his voice is frail and hoarse, a little like Brando's in "The Godfather."

So this is what happens to tipsy, tipplesome merrymakers. They become sad old souls.

Martin's NBC series, produced by Greg Garrison, was never very good, and the skits-in-clips hailed by Welles as "some of the best comedy ever to grace the television medium" (the gods will have a good cough when they hear that one) prove predominantly shrill and forced. Lesser stars like Ruth Bui do all the work while guest potentates like Frank Sinatra bask in phony show-bix obeisance and cling with Martin to the cue cards just out of the frame.

One of the few brights spots on the old Martin variety hour was his crooned ballad at the piano, usually preceded by a surprise, or mocksurprise, comedy bit. The one recalled on the special tonight is especially mirthful; Jonathan Winters comes in for a landing as Maude Frickert. To Martin, Maudie coos, "Take me to the House of Pies."

If the Martin variety show was hardly a TV landmark, a subsequent format, the Dean Martin weekly "roast" of a guest celebrity, was genuinely corrupt. All the jokes got roars on this prefabricated blowout because Garrison was a master of the canned-laughter machine and manipulative tape-editing: shots of cronies on the dais, chortling to beat the band, were inserted regularly during the joke-telling, whether the guests had actually been laughing at the joke in question or not.

Welles says the first roast was given for then-governor of California Ronald Reagan. But they don't show a clip from that one. They show a long, drawn-out, unfunny routine by Peter Falk as Lt. Columbo, all but kissing the footsies of the honoree, Sinatra (Reagan can be seen laughing in one brief shot). Few television spectacles can equal this in terms of eliciting sheer and deeply felt disgust.