The Scholars of Cambrai, one of the better local a cappella choruses, live up to their name with this exhaustively researched program on music and politics in Renaissance Florence. The political life of that city in the 15th and 16th centuries, of course, revolved around the scheming Medici clan, who, as it turned out, also had a taste for music. It was the Medicis who imported Franco-Flemish composers to liven up the local music scene and to enhance their own prestige among the nobility of Italy, and some of the family even indulged in music making themselves. Lorenzo the Magnificent, for instance, played a bowed string instrument suspected to be a precursor to the violin and wrote lyrics. Included in this concert are laments and carnival songs by Lorenzo set to music by Heinrich Isaac; "Nuper rosarum flores," written by Guillaume Dufay for the dedication of Brunelleschi's Cathedral of Santa Maria del Fiore; and a vernacular religious song with words by Savonarola, the Jesse Helms of Florence, who reigned during the last republic. Other composers represented are Bernardo Pisano, Philippe Verdelot, Jacob Arcadelt, and Francesco Corteccia, who was Cosimo I's court eulogizer. The eight-voice choir will perform under the direction of Gail Gillispie. Fri- day, 8 PM, Seabury-Western Theological Seminary, 2122 Sheridan, Evanston. Saturday, 8 PM, St. Josaphat Church, 2311 N. Southport. Sunday, 3 PM, Augustana Lutheran Church of Hyde Park, 5500 S. Woodlawn. 268-9879.