"Rockette: A Holiday Tribute to the Radio City Music Hall" should really have been titled "The Mausoleum Follies." The "showplace on the nation" never looked more like its own tomb than in this pallbearing NBC special.

Empty old theaters may be apt settings for murder thrillers, but not for musical specials; co-stars Ann-Margret and Gregory Peck-what a toe-tappy twosome, they-rattle around the Music Hall like decrepit tots locked in after closing. The special, at 9 tonight at Channel 4, makes a better argument for closing the place down than for enlisting civic funds to keep it alive.

Producers Gary Smith and Dwight Hemion-Hemion also directed, in a velvet fog-missed two crucial charms about the musical Hall. One is that it was designed to be filled with people; when its 5,000 seats are eerily empty, it is not fun house, and dubbing in a fake L.A. audience's cheers and whistles is of no help.

Also, until its management turned crybaby over economic woes in recent years, the Music Hall always appeared comfortingly oblivious to the world outside. It had a golden mediocrity all its own. The writers of the special chose to get topical, however, and invented the feeble device of having Alan King, never less funny, pope up here and there as a newsdealer spouting specious social history.

Ann-Margret romps in her increasingly geriatric style through a number or two-one a leaden misconception about a Rockette who learns that her boyfriend has been killed in World War II but goes on stage for a toy soldier routine anyway.

An attmept to simulate the classic Mern-Martin duet by teaming Ann-Margaret with Beverly Sills, who is still running for the post of National Good Sport, falls flat, but Greer Garson does a brief and hilarious self-parody full of extravagent gestures and Miniveresque head tosses. Not even Carol Burnett coul dlampoon Greer Great Lady so with such zest.

The program ends with Peck Joining his costar for "Have Yourself A Merry Little Christmas," and Peck's croaky stab at singing is somehow more effecting than Margret's embalmed professionalsm. It does not, however, save what was meant to be a bash from coming across as an obbit.