In the early 1950's, she began using 12-tone techniques, principally as a way of creating themes rather than as an escape from conventional tonality.

Mr. Perle's compositions provide ample evidence that music can depart totally from conventional tonality, be highly systematic and yet rewarding and understandable to the lay listener.

For although the pieces occasionally strayed into the realms of atonality, symphonic jazz and exotic modalism, their common ground was conventional Western tonality.

Vibrant and edgy as his early pieces were, however, they retained their connections with conventional tonality, and several of them, including the First Symphony, were successful from the start.

The conventional scale, if not conventional tonality, made a few appearances.

Stravinsky and Schoenberg, the two great pioneering composers of the early 20th century, whose explorations compelled them to abandon conventional tonality, understood this point, Mr. Boulez notes.

Freedom is what many younger composers are striving for, and the tyrannies of the 12-tone system and Minimalism - or of conventional tonality, for that matter - cannot provide it.

Nothing else on the program was quite that simple or direct, although Robert Erickson's "Two Songs" (1986), which Sasha Cooke, a mezzo-soprano, sang ravishingly, kept conventional tonality well within its sights.

Generally, however, his music is rooted in the 19th century, yet exhibits independence of form, ranging from extremes of conventional tonality to frequently polyphonic chromaticism, nonetheless never metamorphosizing into atonality.

In 1930, he met Berg, Anton Webern and other Schoenberg students in Vienna, and was immediately taken with Schoenberg's 12-tone technique, a way of organizing themes that avoided conventional tonality.