When the distinguished British choral conductor David Willcocks made his local debut with His Majestie's Clerkes two seasons ago, he received standing ovations. Head of the Bach Choir of London and a celebrated organist, Willcocks combines musicianship and scholarship in his approach to prebaroque vocal music--as fans of his popular recordings with the King's College Chapel Choir already know. And he's reportedly an eloquent champion of the music of William Byrd, England's greatest composer before Purcell. It will be interesting to see how he and the Clerkes handle Byrd's (underrecognized) masterwork Mass no. 3, the main attraction in this concert showcasing several of the great composers of the late Renaissance. Byrd, an adept contrapuntalist and a prolific innovator of liturgical music, wrote the mass as a challenge to performers. Also on the program are motets by Gabrieli, Palestrina, and others--paired with settings by Byrd of the same texts. These a cappella pieces range from four-voice works to some for eight-voice double choir, and together they ought to amply show off the talents of the Clerkes, one of the finest vocal ensembles in the Chicago area. Tonight, 8 PM, chapel, Archbishop Quigley Preparatory Seminary, 103 E. Chestnut; Saturday, 8 PM, St. Luke's Episcopal Church, 939 Hinman, Evanston, 708-866-7464.