Jazz, which is forever making a comback, has never really gone away. Its audience is intensely loyal, its artists admirably dedicated; all it lacks is the popularity of rock and the respectability of classical music. Which, some would argue, means that it lacks everything. For with neigher one nor the other, it seems always condemed to cult status.

Nobody is satisfied with this, least of all the jazz musicians. They are pushing, on the one hand, toward some sort of rapproachment with rock in hopes of attracting the same sort of mass audience; and on the other, in the direction of the classical avantgarde, supposing that by reducing jazz's audience even more drastically they may give it art status. A few rare individuals, such as keyboard man Chick Corea, have moved alternatively in both directions.

For the most part, jazz critics have encouraged the latter tendency while denouncing the former. Only a couple -- I am one -- reverse this, supporting the jazz-rock fusion and rejecting the avant-garde bargin in nearly all its manifestations. Michael Ullman, who writes on jazz for The New Republic, is a kind of Chick Corea of the critics, for he manages to look in both directions at once and keep right on smiling.

As a matter of fact, the eclecticism of this collection of his criticism, "Jazz Lives," is one of the things I like best about it. He is able to write knowledgeably and with enthusiasm on the late Joe Venuti, who, when he died a couple of years ago, was probably the oldest active jazz musician; and then turn around and give the same sort of keen appreciation to avant-gardists such as Anthony Braxton, Sam Rivers, and the late Charles Mingus. And he does not, as so many other critics have, automatically put down the great tenor saxophonist Sonny Rollins for trying to reach a large audience, or reject the late Rahsaan Roland Kirk for his bizarre displays of saxophone showmanship.

Perhaps the most important reason for this is suggested by the title of this book, "Jazz Lives." Ullman uses the interview-profile format in nearly all of these pieces. He is out to understand not just the music, but also the men and women who make it. What he gives us is not pure criticism, but morsels of analysis and commentary served up between generous slices of biography.

And through these specific cases he deals with the jazz life in general. That it can be a hard life should be evident from my frequent use of "the late" in mentioning some of the artists Ullman writes about. There are references by him, and sometimes by the musicians themselves, to periods of heroin addiction and to bouts with alcoholism.

But the life has its compensations. That fine jazz pianist, Marian McPartland, as verbally articulate as she is musically fluent, puts it all quite positively when she tells about talking to parents who are dead-set against their kids becoming jazz musicians: "They always think of the worst aspects of things: poverty, meeting undesirable people, bumming around. . . . Well, I think musicians are a rare breed who are working at something they really like to do. You see so many people for whom the word 'work' conjures up something unpleasant, whereas for us, going to work means something pleasant . . . As far as I'm concerned, it was never work. It's usually fun."

It would be even more fun if it did not demand such sacrifices, if the business end of it were not stacked so unfairly against the artist. Michael Ullman recognizes this, and some of the best pieces deal with some of those who have worked hard to make the jazz life easier, more equitable and rewarding for the musicians: with Maxwell Cohen, the New York lawyer who was responsible for getting the city's damnable "cabaret card" regulation abolished; with John Snyder, whose Artists House record label is at last giving Maxine Gregg, who handles the musicians she represents with fairness, flare and aggressiveness; and with Steve Backer, a rcord producer who is out to prove that jazz can make money for the company that releases it and for the artists who record it.

My only complaint about "Jazz Lives" is that Michael Ullman might have spoken a little more often and emphatically in his own voice. While the interview format works beautifully with some of his subjects -- with McPartland, Horace Silver and Tommy Flanagan, to mention just a few -- it is not always quite suitable to others. Jazz artists are not always completely aware of what they are up to, or are sometimes a little reluctant to say.

In many ways, the best thing in the book is Ullman's eight-page introduction. In it, he deals at length with the contradictions implicit in the music and with society's attitudes toward it -- contradictions that must be reconciled if this great and distinctive art form is to survive.