CAMBRIDGE — Sacred and secular were, in the 15th century, not as oppositional as they seem today. Just consider the heavy yet heavenly figures of Italian Renaissance artist Piero della Francesca. Or the music of his Franco-Flemish contemporary, Johannes Ockeghem, as presented by the local Renaissance choir Blue Heron Saturday at the First Church in Cambridge, Congregational.
The title of Blue Heron’s program, “Divine Songs: Connections and Exchanges Between Secular Song and Sacred Music,” was deceptively simple. In the 15th century, it became common for composers to use secular songs as the basis for their Masses and motets. (The hit tune of the century, “L’homme armé,” turns up in more than 40 such settings.) Ockeghem used his own secular compositions as the basis for a number of his Masses, and Blue Heron allowed us to hear that by presenting first the parent song and then part of the Mass it gave birth to. Ockeghem’s “Ma maistresse” began the program and was followed by the Kyrie and Gloria from his Missa “Ma maistresse.” What’s more, the songs Blue Heron chose themselves mix sacred and secular. The “mistress” for whom the frustrated lover of “Ma maistresse” weeps could be a courtly lady, or she could be the Virgin Mary; the grief-stricken woman in “Fors seullement” might well be Mary addressing Jesus.