Medieval instruments will play medieval music in a concert conducted by Paul Hindemith, Charles Eliot Norton Professor of Poetry, tonight at 8:30 p.m. in Sanders Theatre.

Hindemith will use only authentic medieval instruments or modern copies loaned by the Metropolitan Museum of New York and the Boston Museum of Fine Arts. Most of the performers are students in Hindemith's class on the History of Theory.

A composite Mass made up of selections from different composers will be one of the evening's highlights. William Hess of New York, famous minnesanger and troubador singer, will head the list of soloists. An all-male chorus and three soloists will sing an organum by Perotini.

The final number of the evening calls for audience participation in a canon by Dufay called "In the Manner of Trumphets." Two trombones will play antiphonally while the audience will sing their respective voice parts as written on the program.