"Hal Linden's Big Apple Starring Hal Linden," as the announcer calls it, is not so much musical entertainment as incitement to narcolepsy. The problem for producers Ken and Milzie Welch was to devise a TV special so dull that Linden could take the foreground by default, and for what it's worth, they managed.

The camera keeps Linden front and center and guest starts in distant subservience, as the hour slumps forward tomorrow night at 8 on Channel 7. Perhaps the star of ABC's "Barney Miller" has a clause in his network contract that guarantees him an hour each season in which to conclusively demonstrate his strictly imaginary prowess as song-and-dance man.

How insecure are the semitalented. The principal recurring joke of the show -- a filmed musical tour of Linden's home town of New York -- involves the failure of people on the streets to recognize this famous, famous person. Imagine being so out-of-touch that you don't know Hal Linden when you see him! Oh, ho-ho!

There isn't much here on the humor side, though that old wheeze about the designer original that turns out to be a mass-produced frock at least leads into a number by the Rockettes, shot in the street at Rockefeller Center right beneath Freddie Silverman's window. Boy, he must have been sore.

The producers toss Linden into the middle even of this smash act, however, and other guests, like Robert Guillaume and Shecky Greene, are relegated to second-banana servitude. When the hour is not functioning as Linden's personal publicist, it becomes a deceptive travel poster for a scrubbed-up New York. Either way, "Hal Linden's Big Apple" is Sominex City.