The following is excerpted from a superb article on Bach written for The Hudson Review by Harold Fromm, Visiting Scholar in English at the University of Arizona:
Bach wrote his keyboard and organ music for instruments capable of linear performance only, uninflected by touch. The excitement that Romantic and contemporary music derives from touch-sensitive “expression” on pianos was in Bach’s day composed into the linearity itself and abetted by performance practices. It must have been his concern to sustain notes on the fast-decaying harpsichord sound (so easy to do with organ pedals) that prompted him to bring the use of the thumb into greater practice. As the “Obituary” reports, “Before him, the most famous clavier players in Germany and other lands had used the thumb but little.” But as anyone who has played preludes and fugues from The Well-Tempered Clavier knows only too well, the thumb (and the little finger) is critical for holding down a key while the other fingers play around it. Beyond this, the composer could add more notes to chords to increase their density and weight. He could add arpeggios and figurated strummings to sustain sounds beyond the capacity of a mere thumb. On the player’s part, speeding up and slowing down could alter the adrenaline level, so to speak. Distending the tempo so that notes are played a bit late (after the beat) or early could provide tension and emphasis. Using two keyboards could introduce contrasting timbres. Bach’s Italian Concerto provides a perfect demonstration of all these qualities, with furious propulsion punctuated by dense chords in the outer movements and arioso lyricism in the middle (exploiting two keyboards), written into the music, no “expression” needed, just the player’s skill on the harpsichord. An “expressive” piano performance that turns it into one of Mendelssohn’s Songs Without Words subverts its most distinctive and powerful properties. The best recording-era performances I know of The Well-Tempered Clavier’s forty-eight preludes and fugues (and much else) were done by Wanda Landowska fifty years ago. Although critics made fun of her large Pleyel harpsichord (which could be said to have reintroduced the harpsichord in modern times), their objections nowadays seem pretty feeble. They tended to zero in on the 16-foot stop that gave her instrument a powerful bass, whereas harpsichords mostly have 4- and 8-foot sets of strings, named for their organ pipe counterparts, though they are nowhere near those lengths. But in Bach’s day, besides the usual cembalos (as harpsichords are called in European languages), there were pedal harpsichords, however rare, that made use of foot-played organ-like keyboards on the floor for deep bass. So the effect produced by Landowska’s Pleyel was hardly unprecedented. And, of course, playing Bach on today’s grand pianos is much more egregious. Landowska’s Well-Tempered Clavier revealed more of the music more powerfully than anybody else, squeezing out every drop of its seemingly inexhaustible juices. Although much credit must be given to Glenn Gould’s astounding attempts to make the piano sound as astringent as possible, presumably like a harpsichord, one can only wonder if the effort was really worth it when modern harpsichords do it ever so much more effectively. [All emphases mine.]
The entire Fromm article can be read here, and worthwhile reading it is, too.
(Our thanks to the always indispensable Arts & Letters Daily for the link to the Fromm article.)