There is a lot to enjoy in " 'Follies' in Concert," which airs tonight on PBS (Channel 26, approximately 9 p.m.). But you can catch most of the good stuff -- the songs of Stephen Sondheim, who is equally talented with lyric and music -- if you tune in 45 minutes late.

Besides the musical numbers, which are presumably what it is all about, " 'Follies' in Concert" devotes an enormous amount of time and energy to celebrating the sheer glory of itself. It is not only a musical show but a documentary about the musical show. Like so many of Sondheim's songs, Sondheim's video extravaganza focuses tightly on exploring and explaining itself.

The concert commemorated in this presentation was undoubtedly one of the major media nonevents of the 1980s. An all-star cast included such names from show biz as Comden and Green (performing someone else's music), Lee Remick, Carol Burnett, Andre Gregory, Barbara Cook, Phyllis Newman and Elaine Stritch. The concert was assembled at Lincoln Center for a single, nostalgic performance of a Sondheim show that had not done well enough the first time around to satisfy him. It was a classy event, worthy of Lincoln Center. The orchestra was the New York Philharmonic, no less, and the singers included not only Broadway types but also operatic notables of the past (Licia Albanese) and the future (Erie Mills).

The whole thing was thrown together in four days; everybody is very proud of the fact and keeps talking about it. The bustle, turmoil and confusion of the process are thoroughly documented in shots of rehearsals, planning and discussion that take up a lot of on-screen time, along with views of people getting out of taxis, backstage hugs, mounting tensions and all the other standard apparatus of the "no-business-like-show-business" theme.

Actually, as Sondheim admits on camera, the whole thing was done simply "to get a definitive recording of the score." That was accomplished, and the songs make it seem well worth the effort. They also make you want to buy the record, and that may be partly what this was all about.

Like so much of Sondheim's work, the title of "Follies" cuts in several directions. It is the story of a group of old troupers getting together to do one last, nostalgic performance of a variety show before it passes into oblivion. The "follies" in the title are not only the name of the show but a description of the life styles of various performers. A substantial part of the show's original interest was focused in the interaction between the on-stage material being performed and the offstage lives of the people performing it -- people with "one foot in the past and one foot in the present."

Phyllis Newman sums up some of this dimension in her description of her "mirror song," "Who's That Woman?" The song, she says, is "about wasting your life . . . then recognizing who you are and what you are at a certain age." Otherwise, much of this dimension is lost in this production, which trims away most of the spoken dialogue and substitutes nearly an hour of celebrity-watching under the guise of documentation.

Still, the music is worth waiting for. Newman is excellent and so are Stritch, Burnett, Remick and most of the others. But for this viewer the best moments are Barbara Cook's singing of "Too Many Mornings" and "I'm Losing My Mind." Those who agree with this judgment should stay tuned through the show's endless final credits for the hour of undiluted Barbara Cook that comes immediately afterward.