More than 200 undergraduates this spring will participate in the performance of a Harvard instructor's musical mass about the development of the atom bomb.

Members of three Harvard choruses, the Harvard-Radcliffe Orchestra (HRO) and two Boston singing groups will perform the "Trinity Mass" at Sanders Theater and then travel to New York City for a performance at the Cathedral of St. John the Divine.

Senior Lecturer on Music James D. Yannatos wrote the mass and will conduct the two performances April 11 at Harvard and April 12 in New York.

In addition to the text of the traditional Latin mass and Biblical quotations, the composition includes lyrics from children's poems, recollections of Hiroshima survivors and excerpts from Robert J. Oppenheimer's 1954 testimony before the Atomic Energy Commission.

Despite its solemn subject matter, Yannatos said the piece is about hope. He cited a line from the last part of the 80-minute chorale, "I dream of the day when my child will say `What was war?"'

"As a citizen of the 20th century living with the anxiety caused by the atomic bomb, I felt compelled to write this piece as a musical and social statement," Yannatos said.

Yannatos frequently sang Gregorian chants and masses as a boy soprano, and he has remained interested in the musical form.

Although professional singers will perform the solos, members of the Harvard Glee Club, the Radcliffe Choral Society and the Collegium Musicum will form the chorus during the April performances.

The Back Bay Chorale and Youth Musica, two Boston singing groups, will also participate.

Private donations will pay for transportation costs and soloist fees, while ticket sales should cover the remaining expenses, said HRO Director Benjamin A. Loeb '87.

Several students who will perform the piece yesterday praised its message, although they said it is very difficult to sing.

"It's not really beautiful, but it definitely makes a strong statement. It is an important piece which draws all of the singing groups together," said Juliana C. L. Chen '87, a member of the Collegium Musicum.

"I hated it when we started it, because it is so hard to sing. It jumps around a lot. However, it is a really beautiful, intellectual piece," said Deborah L. Levi '89, another Collegium member.