With the incredible growth and expansion of the City Musick since its 1985 inception, it's easy to forget that there is another period instrument ensemble in Chicago that is one season older: Basically Bach. The City Musick is trying to build a permanent orchestra of Chicago-area players; Basically Bach hires many of its players from outside the area and is really more of a Baroque music presenter than an ensemble. Still their programs can be very rewarding, and their opening concert looks particularly interesting--a wonderful starting point for those new to Baroque music or authentic performance practices. Entitled "The Sparkling Baroque," the cornerstone of the concert will be one of the most jubilant and festive of the Bach cantatas: no. 51, "Jauchzet Gott in allen Landen." The work will spotlight the interweaving lines of soprano Carol Loverde and trumpeter Fred Holmgren. Tonight, 8 PM, Saint James Cathedral, 65 E. Huron; Saturday, 8 PM, First Congregational Church of Evanston, 1417 Hinman, Evanston; Sunday, 7:30 PM, First United Church of Oak Park, 848 Lake, Oak Park; 508-0635.