The churning, rheumatic mechanism of a harpsichord — notes needling your ears like drops of acid rain — doesn’t necessarily play well to an audience whose sensibilities have been moulded around the picture-perfect delicacies of the classical piano. J.S. Bach’s freakishly popular Goldberg Variations remains best known through the recording made by the oddball Canadian pianist Glenn Gould in 1955, a record that would bleed unexpectedly into mainstream consciousness.