The weekly Dame Myra Hess concerts at the Cultural Center have been around for so long–well over a decade–that we take them for granted. But in how many other North American cities can one regularly hear accomplished musical performances without having to pay? While any music lover who’s downtown during lunch hour on Wednesdays should make a habit of attending these concerts, I’m singling out this recital because (1) Mark Kroll is a first-rate, much-recorded harpsichord player and scholar; (2) harpsichord music sounds especially pleasing and authentic under the dome of Preston Bradley Hall; and (3) the program of Francois Couperin’s Sixth Suite followed by Bach’s French Suite in B Minor makes musicological sense: Bach wrote his suite as homage to Couperin, who was grand organist to Louis XIV, the author of a famous book on harpsichord playing techniques and composer of more than 230 pieces for the instrument, and a giant in his time unjustly overlooked today. Wednesday, 12:15 PM, Preston Bradley Hall, Public Library Cultural Center, 78 E. Washington; 744-6630 or 346-3278.