FACE IT, kids, Hair is going to be around longer than any of us. "The American Tribal-Love Rock Musical" has already settled down for long, long runs in New York, Paris, Chicago, San Francisco, Las Vegas, London, Tokyo, Sydney and now Boston. It will soon hit such places as Seattle, Honolulu, Memphis, Washington. Tel Aviv and God knows where else. I suspect that by the time we are approaching senility Little Rock, Peoria, Salt Lake City, Gstaad and Darien will all have their own Hairs. (Or, to put it another way, if you don't go see Hair, stick around long enough and some day it will come and see you.)

You can, if you like even make a career out of seeing this musical. Clive Barnes has. That man goes all around the world to see the different Hairs and has at last count written eight reviews of the show. All raves. Mr. Barnes. of course, writes for the New York Times and that leads us to believe that any love-rock show he likes must be middle class, commercial, sate and silly, Well. that's true- Hair is all those things. Yet. despite that. Hair is a phenomenally exciting piece of theatre. Somehow it works-but why it works is anybody's guess.

Perhaps a description of the work would be as helpful as anything. Hair consists of about 40 hippie-looking singer dancers who spend two hours and 45 minutes telling bad jokes, singing about 50 songs, running into the audience, burning incense, petting, dancing and jumping. It all looks improvisational-but the spontaneity of Hair is actually a by-product of the ingenious (and disciplined) staging devised by Tom O'Hargan. There is a script, but the plot (Claude, a boy from Flushing who likes to think of himself as being from Manchester, England, gets drafted and is killed in Vietnam) is hardly noticeable. There is social criticism (peace), but there is no ideology. There is rock music, but it has no acid to it. What can you say.

For one thing, I could point out that at the end of the first act, the cast takes off its clothes. You've heard that before? It's still important. The strip scene occurs during the climax of a song Claude sings called "Where Do I Go?" He has just received his draft notice, burned his draft card, and he is now asking fiercely. "Is there an answer/in [lovers'] sweet faces/ that tells me why I live and die?" There is a rumble underneath the tarpaulin covering the stage below him. Heads poke out, and arms, waving, reaching. The Hair tribe is nude, facing us. The act has only the logic of despair, but it is not gratuitous. It is only right that they have taken off their clothes. It is a sad and angry gesture: if you are the right age in the right mind, you might cry when it takes place.

The end of the second act, after Claude has been killed, is similarly charged with ferocious and theatrical vibrations. The song this time is "Let the Sunshine In"- and the cast sings it on the edge of the stage, shouting the words, jumping up and down. barely controlling what seems to be a desire to throttle the audience into submission. While the number may mean nothing out-side the theatre, within the show it is potent enough to make you want to kill anyone who ever thought for a second that Vietnam was right.

The success of these and the many other electric moments in Hair is due as much to the music (by Galt MacDermott) and lyrics (by Gerome Ragni and James Rado) as to the staging. While the songs are definitely of a now-dated rock genre, there is no denying that many of them are great theatre pieces. The comedy numbers (a Supremes satire called "White Boys." "Initials," "Sodomy") are far funnier than anything in the book (written by the co-lyricists). And some of the more romantic songs are sweet in the best sense of the word: Claude sings when we meet him, "I believe in God / And I believe that God / Believes in Claude / That's me."

THERE is little to say for the Boston production except that it is very fine. James Sharman has recreated O'Horgan's staging so well that I couldn't tell much difference between this Hair and the O'Horgan-directed Hair I saw in London last summer. (Sorry, but I can't compare the Boston company to the New York one, as I have not seen the original Broadway Hair. ) Some of the jokes have been updated (references to Nixon and peace symbols abound more than ever), and the singing voices of the leads-all unknowns-are exceptional.

So there you are. It may not be high art. it may not be camp. it may not even be "Tribal-Love Rock"- but who has the right to complain? Hair is the biggest institution to sweep America since the flag, and in its presence you have no choice but to salute.