Expression pedal
From Wikipedia, the free encyclopedia
Expression pedal is an important control pedal found on electronic and pipe organs and many digital synthesizers.
The loudness, or volume, of a note on a pipe organ and older electronic organs has no relationship to how hard its corresponding key or pedal is struck; in other words, the organist produces the same volume whether he/she depresses the key or pedal gently or firmly. The tone will continue to sound, moreover, for as long as the organist holds down the key, with no natural end or decay. All of this would lead to a very flat, undynamic sound without the expression pedal, which literally allows the organist to make her music more “expressive” and dynamic by altering the volume as she plays. The expression pedal also allows the organist to compensate for the fact that the organ grows louder if more than one note is sounded simultaneously (i.e., chords or polyphony).
On early pipe organs, a division of pipes would be enclosed in a swell box, one part of which would consist of shutters or slats. The expression pedal would open or close these slats, effectively adjusting the music’s perceived loudness. Because of this function, the expression pedal is sometimes known as the swell pedal.
The expression pedal itself is a large pedal, roughly resembling an oversized automobile accelerator, either partly or fully recessed within the organ console’s kickboard and located either above or to the right of the organ's pedalboard. Operation is straightforward. The organist places her entire foot on the pedal; as she plays, she presses forward and down with her toes to achieve greater volume, and presses down with her heel to reduce volume. At or near the maximum setting, her heel may lift off of the pedal, leaving only her toes in contact with it. In other instances, if the organist is engaged in playing the pedalboard with both feet and needs to make a rapid dynamic change, she may work the pedal with only her toes, though this gives less precise control over the dynamics.
With some musical genres, the organist may rest her foot on the pedal constantly, pumping it up and down either gently or more forcefully as she plays to achieve crescendo and diminuendo. In other styles that have little dynamic variation, however, she may remove her foot from the pedal after her initial adjustments. Unlike an accelerator, the expression pedal is weighted so that it stays in the position at which the organist sets it until she adjusts it again. This allows her to remove her foot once she has adjusted the volume, permitting her to use both feet to play the pedalboard.
Reed organs of the late nineteenth and early twentieth centuries substituted a pair of bellows pedals for the pipe organ’s expression pedal. By constantly pumping the pedals up and down vigorously, the organist forced air across the organ’s reeds to produce sound. This self-powering feature made the organ widely available to homes and small churches, though the dynamic range tended to be limited and eventually the organist would tire from the pumping. Subsequently the electrically powered reed organ, and later the electronic organ, replaced the bellows pedal with an expression pedal, which allowed the organist to effect a substantial change in volume merely by slightly changing her pressure on the pedal.
Popular organ music of the twentieth and twenty-first centuries such as jazz, has a highly dynamic style that requires constant use of the pedal in a fashion very different from that of classical literature. This tendency increased with the arrival of spinet organs and modern synthesizers, which offset the expression pedal and reduced the size of the pedalboard. These changes meant that the organist could play the pedalboard with only her left foot, encouraging her to keep her right foot on the expression pedal all during her playing. This arrangement naturally encouraged her to pump the expression pedal slightly as she played to accent her phrasing, thus making her music much more dynamic than classical organ repertoire. To take advantage of this style of playing, some expression pedals on modern electronic organs are equipped with toe switches. These allow the organist to make quick registration or tempo changes by using her toes without moving her foot from the pedal.
Larger pipe organs may have two or more expression pedals to control the volume of different divisions individually. Expression pedals may be non-linear in response, meaning that slight pressure changes may cause a greater proportional change in volume than a more complete depression. In this regard each organ tends to be rather distinct.
On pipe organs the expression pedals should not be confused with the crescendo pedal, which progressively adds stops as it is depressed.
