HELLO DOLLY! - At the National through November 12.

When "Hello, Dolly!" first came to National Theater, in 1964, it was merely a musical comedy. Now it's back as a Beloved American Institution. There are advantages to seeing it in either of these two manifestations, but they are not quite the same experience.

The first time, there was the delight, particularly fresh since it was a pre-Broadway run, of the birth of a good musical, with all the charm of just-minted hit songs and the integration of music and humor. Now there are no surprises. Each well-known moment is cheered before two notes are out - greeted with loving respect to its prolonged health.

The James M. Nederlander and Houston Grand Opera production is anything but your shop-worn road company. With last year's operatic production of "Porgy and Bess," it's part of a planned quality revival of American musical favorites.

And it has the original Dolly, Carol Channing, still champion as other star-Dollys have come and gone. In fact, the the joy of showing "Hello, Dolly!" to a new generation is not so much to have them to see a delightful musical, but to see what a true musical star is in the theater. The body mikes have taken over in the intervening years, but Carol Channing can still fill a theater with the headlight beam of her eyes, and her voice, aside from amplification, is an up-to-the-second-balcony type that makes any line riveting. When she instructs a young man how to place his feet for dancing - "left foot there, now right," or whatever - it is spellbinding.

Nevertheless, displaying "Hello, Dolly!" as a sort of classic invites the kind of scrutiny that would be inappropriate and even ungrateful in looking at unpretentious entertainment. And "Hello, Dolly!" does not have the emotional force, either in music or plot, of "Porgy and Bess." "The Matchmaker," from which it is taken, states the Thornton Wilder philosophy of life-must-go-on in a rather slight manner.

But it certainly does make a good musical comedy.