The Tallis Scholars, hailed as "a capella superstars'', have performed to standing room only audiences across the United States since their American debut tour in 1987.

The London-based ensemble, under the masterful direction of Peter Phillips, appeals not only to early music enthusiasts who search for musical and vocal purity, but also to first time listeners who are struck by the sheer beauty and power of the sound.

Much of their programme on Monday evening was devoted to the works of the Italian Giovanni Pierluigi da Palestrina. A most prolific composer, the exact date of his birth is unknown, but it is thought to be 1525. Since he died in 1594, this is the 400th anniversary of his death. It is ironic that, in the 20th century, with its technology, `state of the art' constant boast, in terms of choral complexity and vocal supremacy, a return to the 16th century is the perfect musical consummation.

After setting the scene with the introductory Plainchant "Veni Creator Spiritus'' the choir performed Palestrina's wonderful "Missa Veni Creator Spiritus. Palestrina com posed 104 settings of the Mass of which only a few are heard regularly. The Tallis Scholars have done much to revive interest in his work. From the outset, we were aware we were listening to the very essence of musical refinement. As Pope Julius II commented to the composer, "The law, my dear Palestrina, ought to employ your music to lead criminals to repentance''. Certainly, as performed by The Tallis Scholars, the "Missa Veni Creator Spiritus'' was of unearthly beauty...an inspiration to all those present.

The ten singers, five women and five men, present a wonderful blend of sound and sing as one perfect instrument. Despite the historical irregularities (Palestrina would not have employed ladies, but boy sopranos) the tone quality is absolutely authentic. It is, of course, slightly more robust at times since we are dealing with mature female voices, however well managed, but this only serves, if anything, to enhance the overall effect.

After the intermission we heard the famed Miserere by Allegri. This sublime work was for many years never performed outside the Sistine Chapel. The youthful Mozart, on visiting the Vatican, heard the piece once and immediately wrote it out from memory. Far from being censured for breaking the monopoly on the "Miserere'', the Pope awarded the fourteen year old genius the title, "Knight of the Golden Spur''.

In performance, The Tallis Scholars sang antiphonally with a quartet including the leading soprano in the gallery. The effect was quite thrilling with that wonderful top C floating effortlessly through the church from apparently celestial forces.

A cappella singing of this style is most demanding with tremendous physical and intellectual resources needed at all times. The intricate vocal lines are transparent and leave no room for error. It was obvious on Monday evening that we were in the presence of not only splendid singers, but excellent musicians.

The programme ended with four works by Palestrina, "Lamentations'', two settings of "Alma redemptoris mater'' and "Magnificat septimi toni'', the latter an emphatic and vibrant conclusion to a superb evening of world-class choral singing. MARJORIE PETTIT.