When Anthony Braxton acknowledges applauses he often did yesterday afternoon in his solo jazz concert at the Washington Project for the Arts--he gazes above his audience and nods humbly, politely. Even between numbers the alto saxophonist's concentration is absolute, making him appear aloof at times. But several of the brief pieces he performed gave lie to occasional criticism that his music, too, is unrelentingly austere and detached.

There was nothing unemotional, for example, about the way Braxton took a simple, repetitive figure and, by constantly and forcibly recycling his breath, transformed it into a juggernaut of sound. Or the way he imposed a gentle swing pulse on some pieces, or illumined others with a warm, lyrical tone. As Braxton knows, solo jazz concerts are fraught with dangers, and he avoided most of them by keeping his selections short, focused and varied.

Whatever the mood of the pieces, Braxton was full of surprises. The displacement of rhythm, silence, dissonance and counterpoint figured prominently in each of his works, and although some of the wheezing effects he employed grew tiresome, Braxton consistently struck a balance of freedom and form.

Trombonist George Lewis, who was scheduled to perform wth Braxton, did not appear for the first of the afternoon's two concerts.