Charles Wuorinen takes a professional view of his work, which is composing music. "People commission you to write a piece," he said last night in the Terrace Theater, "and they ask you to make it 15 or 20 minutes long. Apparently, they don't realize that the difference between 15 and 20 minutes is likely to be three months' work."

At a rate of about 5 minutes every three months, Wuorinen presented perhaps three years' worth of music last night in the Kennedy Center's American Composers series. If that sounds mathematical, so did some of the music. And if it didn't last quite that long, it seemed to.

Wuorinen is one of the most productive composers in America, with more than 150 works to his credit. For last night's program, which included music, a brief talk and a question-and-answer period, he focused on one small corner of his output: music for violin produced between 1967 and 1977. He was the pianist with violinist Benjamin Hudson in his Duo (1966-67), the earliest work on the program, and his Six Pieces (1977), the most recent. Two other pieces, the Violin Variations and "The Long and the Short," were played by Hudson without accompaniment.

Restriction to a single medium and performance in a roughly chronological order served to focus the music's impact and to clarify a development that might be less noticeable in a more miscellaneous program. It confirmed what Wuorinen-watchers have suspected for some time: that this composer -- one of the high priests of serialism and tight, intricate, objective music -- has been subtly changing his style.

The decade covered by these works was the period in which neo-romanticism was launched and began to consolidate its position in American music. Wuorinen has sometimes been considered (although not quite so much as Milton Babbitt) a prime adversary of this movement, and he still talks that way. "I have never been able to distinguish between thought and feeling," he said, adding that he found "thoughts warmer and more exciting than slobbery sentimentality."

There was no slobbery sentimentality in last night's program, but the final work, the Six Pieces, showed considerably more emotional range and intensity than the early Duo or Variations. It was easily the most enjoyable work on the program -- not that Wuorinen considers instant enjoyment something desirable.

Hudson was required to perform some remarkable violin gymnastics, and did them impressively. Wuorinen's piano-playing closely matches his style of composition for the piano.