The left pedal on a piano is usually referred to as the “una corda pedal” by classically trained pianists and teachers, the “shift pedal” by piano technicians, and usually the “soft pedal” by everyone else. If the middle pedal is the most misunderstood pedal on pianos (see The Middle Pedal), then the left pedal is a close second. Let’s begin by clearing up the most common misconception about the left pedal: It is NOT a practice mute. It is an expressive device that gives the pianist a more subdued level of timbre (tone quality) not possible with the hands alone. The difference is so subtle that unless one is playing actual repertoire, one might believe that the pedal doesn’t do anything, or is broken.
The Left Pedal on Grand Pianos
Because grand pianos were the original piano for many years before vertical pianos became available, most piano features were designed on grand pianos first, then adapted to vertical pianos later. In the case of the left pedal, the term “una corda pedal”, or “shift pedal” refers specifically to the way the pedal functions on grand pianos, not on vertical pianos.
Piano strings are arrayed in groups of one string per note (monochords), two strings per note (bichords), and three strings per note (trichords). On grand pianos only, depressing the left pedal causes the entire keyboard to shift to the right (treble) side of the piano a short but noticeable distance (usually about 4 mm, or 3/18 of an inch). This causes the hammers to strike the string(s) with a fluffier, less compacted part of the hammer’s strike surface, producing not just less volume but a sonic shift to a more hushed, ethereal timbre. That sounds like it would be really obvious, doesn’t it? And yet, many people plunking random notes on a piano, comparing how they sound with vs. without the left pedal, claim to notice little or no difference in the sound. It seems that only when playing actual music, especially classical repertoire, does it become obvious that the left pedal offers the pianist a level of timbre not possible without it, almost as if played on a different piano. Some composers explicitly call for the left pedal in the score, but more often than not, pianists will use the left pedal at their discretion, based on the music being played, the unique tonal characteristics of the individual piano, and even the acoustics of the hall or room where the piano is located. In classical piano scores (sheet music), a composer may indicate the use of the left pedal as “una corda” below the staff (or staves), but mostly it is abbreviated as “u.c.”. When the composer intends the pianist to release the una corda pedal, the common abbreviation is “t.c.”, which can be interpreted as tutte le corde (all strings), or tre corde (three strings). These terms date back to Bartolomeo Cristofori, the Italian designer of the prototypical piano, which had only two strings per note. In today’s much larger and more powerful grand pianos with over 200 strings arrayed in groups of 1, 2, or 3 strings per note, the shift pedal doesn’t cause the hammer to hit literally one string, but the original goal of producing less volume AND a shift in timbre is still the same as it was 300 years ago.
The Left Pedal on Vertical Pianos
On vertical pianos, the left pedal rightfully should be called the “soft pedal” rather than the una corda pedal. That is because the left pedal in vertical pianos can only give the pianist access to a level of softness not possible with the hands alone. It cannot change the timbre the way the left pedal on a grand piano can. Because of the way the strings align with the action parts within the confines of a vertical piano cabinet, shifting the action to one side, like with grand pianos, in not an option. Therefore, piano makers had to invent a new way to achieve a similar effect. This is done by pushing the entire hammer line (all the piano’s hammers) closer to the strings. This shortens the blow distance, causing the hammers to strike the strings with less force, thus producing slightly less volume. There is little or no difference in timbre since the hammers are not being shifted to hit the strings with a lesser-used part of the hammer. Regardless, the left pedal on vertical pianos is highly useful in music-making, even if it does not quite equal the expressive subtleties possible with a grand piano una corda pedal.
Hopefully, this clears up any confusion over how, when, or whether to use the left pedal on a piano, what it can do for your music-making, and what it can’t do.
Until next time, thanks for reading.
Paul Yarish, RPT