There is a certain pristine, almost ethereal character that is lost when the superb choirs of Cambridge and Oxford college chapels are removed from their intimate natural settings. One could complain that the 28 men and boys of St. John's College, Cambridge, would have been heard with greater clarity at home than in the vast spaces of Washington Cathedral last night.

Some vocal lines were lost, and diction was blurred by the reverberation. Otherwise, the large audience heard chaste, pure choral music - as they have practiced it for centuries - at its best.

The program was typical. The first half was basically Elizabethan - starting with Gibbons, going on to Byrd and Tallis, with a slight detour to that relative latecomer on the ecclesiastical scene, J. S. Bach.His Fantasia in G for organ was majestically played by David Hill.

Conductor George Guest programmed music of the last hundred years for the second part. Two Latin works by Poulenc and the serene Faure "Cantique de Jean Racine" gave proof that church music has not declined since the days of the old masters.

The wonderful purity of sound that these groups cultivate is unique to Britain. And no one understood that better than the most distinguished English composer in more than two centuries, the late Benjamin Britten. St. John's Choir ought to count him into its future concerts in this country.