Twenty years ago, pianist-composer Cecil Taylor was in the forefront of the jazz avant-garde, shocking listeners with his swelling, dissonant harmonies and thundering, zigzag melodies.

A generation later, he still maintains that position - a lonely perch for a musician who is only beginning to reach sizable numbers of the jazz audience.

But Taylor, who will among the artists performing in the Two Nights of New Music festival opening tonight at Constitution Hall, does not lament his solitary position.

"I just do a musical activity," he says in his clipped accent that's a mixture of Queens N.Y., and Boston. "We come in the world alone and we go out of it alone. In between those times we try to get on as best we can."

Taylor, at 5 feet 6 and 140 pounds, plays the piano as if it were a combination of enemy and friend. Hunching over the keyboard, he sometimes thrashes at the keys, producing torrential sounds bursting out of the limits of methods and harmony. At other times, he caresses the keyboard creating a tortured lyricism.

Taylor's heavy use of dissonance and choppy rhythms has driven many listeners from his performances muttering that his music was "anti jazz."

At one point in the early '60s he earned less that $600 the amount then required to pay federal income tax. But Taylor has persevered.

Has he ever had any doubts about his musical goals?

"I think there are always doubts," he says. "But that is replaced eventually with the recognition that the more you do, whatever it is that you are doing, the better you become. And you attempt to make the music an organic outgrowth of your perception."

Taylor, 44, grew up in a middle-class setting in Long island. He started studying piano early and attended the New England Conservatory for four years. He is as conversant with European classical music, particularlry the 20th-century composers as he is with jazz.

Some jazzmen accuse him of putting too many classical ingredients into his work, especially the influences of Schoenberg and Berg. He dismisses that by saying his music represents his investigation of 5,000 years of musical heritage.

Others criticize him for playing too long. It's nothing for a Taylor ensemble to play one composition for 90 minutes, 45 minutes of which might be a piano solo.

Says Taylor: "I don't know what they are (his critics talking about. They used to say that about (John) Coltrane, but when the rock groups started playing three and four hours that was a ball to listen to. You play as long as you've got material to play - as long as you've got something to say.

"That's why they want to talk about me being a virtuoso piano player. They don't want to talk about the material I'm performing. They use terms like energy. They like to view us as the big black buck."

The pianist has probably found more acceptance in Europe than in his home country. He spent two months touring Europe last spring, and he is scheduled to return next week for a solo performance in Cologne.

Taylor continue to perform in nightclubs even though his music is not especially suited for such a casual atmosphere. "You learn how to play in nightclubs," he explains. "You really deal with people's feelings in nightclubs."

He wants to continue developing. Taylor has written for several dance companies, including Alvin Ailey's and Diane McIntyre's. He'd also like to write for the movies.

"In lots of ways I think I'm just beginning," he says. "There're things I'd like to do now that I had no idea of 20 years ago - and slowly I'm getting a chance to do some of those things."