When the Tallis Scholars sing an encore of "O Praise the Lord. All Ye Heathens," the words are not stern warning but a gentle suggestion. For theirs is a sweet sound, and their concert last night in the comforting austerity of St. Paul's Parish was as warm as a father's embrace.

They are a group of 12 choral scholars visiting from Christ's Church and Magdalene College, Oxford; and from King's College, Cambridge. For this concert, director Phillips Included music by a variety of 16th-century composers, from their namesake Thomas Tallis through the joyful Palestrina. If there was a certain sameness to their singing that belied the rich variety of European music of the period, compensation came in the form of aural splendors. Light, controlled tenors were balanced with remarkably solid countertenor textures; to these were added women's voices that approached the white sounds of treble boys. And when vocal vibrations coincided with timbres happily matched, the sound had an organ's majesty and a lover's glee.

Thomas Tallis, the Gentleman of the Chapel Royal under Henry VIII, was well represented with a opening "Loquebantur variis linguis" and by "Eight Tunes for Archbishop Parker's Psalster." In the latter, which were divided into two sets, the male voices were splendid. The sopranos upset the dynamic balance by pushing the sound in Josquin des Pres' "Benedicta est, caelorum regina," but the doubled tenors soon brought the song under control. Save for the choral beauties of the Kyrie, selections from a mass by Palestrina were the least successful, the Italian master's complex passion not being as precisely communicable as the rest of the evening's repertory.

The Tallis Scholars avoid the mannered diction of so many English groups, expect for the inevitable explosive T's that can be so jarring in Latin. They were precise without being cold, idiomatic without seeming strained. This was rich choral singing of the finest order.