When the Evanston-based chamber choir known as His Majestie’s Clerkes teamed up last year with the Newberry Consort, the joint concert was the early-music highlight of the year. Now the Clerkes have combined a collaboration with gifted local players–in this case the new baroque string ensemble founded by Kevin Mason known as Orpheus Band–with another new tradition: the hiring of internationally established guest conductors. This year’s guest is none other than the extraordinarily gifted British organist and choral director Simon Preston, best known for his tenure as music director of Westminster Abbey, which produced definitive recordings known and respected by music lovers throughout the world. Sparkling clarity and a tightly focused sense of line are Preston trademarks and will be very much in evidence as he leads the two ensembles in a stylish program called “Royal Rejoicings,” spotlighting festive English baroque anthems for double choir and string orchestra by Henry Purcell, John Blow, and Pelham Humfrey. Tonight, 8 PM, Our Lady of Mount Carmel Church, 690 W. Belmont. Saturday, 8 PM, St. Luke’s Episcopal Church, 939 Hinman, Evanston; 708-866-7464.