The Organ, and the Piano

.

I recently rehearsed to myself the differences between organ touch and piano touch; that indefinable quality that enables a good performer to make these instruments sound beautiful.  People who are not knowledgeable about the organ and the piano often believe that the techniques of playing the two are essentially the same.  I can't remember why I thought this a good idea, but perhaps I will remember once I get started...

The organ is really several hundred instruments combined, one for each note.  (Actually, so is a piano.)  They're essentially flutes (or trumpets), and there is a large box full of air (the wind-chest), with hoses connected to each pipe.  When the organist presses the key, a switch opens up the air to that pipe, and it sounds.  For a different note, you press a different key, which sends the air to a different pipe.  The longer the pipe, the deeper the sound.  There is a row of pipes, ranging from a pipe roughly 8 feet long for the C below the Bass Clef, to a little 6" pipe two octaves above Middle C.

The organ can supply different tones by switching on different rows of pipes.  Each row is called a rank of pipes, and the organist gets a rank of pipes ready by pulling out a stop.  So once the "trumpet" stop is enabled (i.e., pulled out), if a C is played, the trumpet C will sound.  Obviously, multiple stops can be pulled, and the note on all the corresponding ranks will sound when played.

In addition, organists can make interesting composite tones by combining stops.  You must have heard octave stops (which play an octave higher, along with the stops that play at "ground level"), super-octave stops --playing two octaves above, and so forth.

A useful way of talking about the octaves is to call the standard octave the 8-foot octave.  One octave higher is the 4-foot octave (or 4' octave), an octave still higher is the 2' octave.  For very serious music, organists will couple in sub-octave stops, 16' for instance, which add notes an octave below the usual sound.

There are other, more amazing notes that take some getting used to; for instance, it is possible to add an octave-plus-a-fifth, which could be, depending on the particular tone of the stop, anything from barely noticeable to highly pungent-sounding, and even more amazing stops.

There are basically two main sorts of pipes: flue pipes, which are basically elaborate whistles, like the instrument called a recorder.  Within this type, there are some sub-varieties: "flute" stops, very wide-bored pipes with a strong fundamental note and few harmonics, in many ways similar in sound to ordinary flutes; "diapason" stops, featuring smaller-bored pipes with a characteristic organ sound, and "string" stops, with very narrow pipes, that give a soft, reedy sound thought to be reminiscent of violin tone (to people with strong imaginations).

The other type is reed pipes, or brass pipes.  These are equipped with a reed that gives these stops a trumpet-like quality, or an oboe-like quality.  A reed is a piece of flexible brass, like the things inside a harmonica.  Reed stops are the trumpet-like stops used when an organist wants a very audible, grand sound.  They're rarely used, unless it is necessary to use a loud inner voice contrasted against surrounding flute voices.

Finally, there are composite stops, consisting of two pipes for every note, each tuned slightly differently from the other, which causes beats when they're sounded simultaneously.  The less said about these stops the better (though they are regarded with favor by a large proportion of organists: vox melodia, vox harmonia, vox celestis, vox humana, and other such voxes are used to describe these awkward stops).

The piano is a very different thing.  Each note corresponds to a string (or up to three strings, all tuned in unison), which is struck by a hammer.  In the harpsichord, it used to be a claw that was dragged past a string, plucking it.  Here, it is a hammer, which must then be quickly removed before it interferes with the string.  The history of pianos is partly the history of the ingenious ways that were found to make the hammer bounce off the string right away: the so-called escapement.  So when you press the key ---and keep pressing it--- the hammer has hit the note and fallen away; the feeling that you're still connected to the note is an illusion.  Of course, once you release the key the dampers come down and silence the string, just as you expect.  (One of the cleverest bits of invention in pianos is the ability to play quick repeated notes.  The hammer falls away after the first note, but is kept ready for a subsequent note, just in case it is needed.  Once the key is completely released, the hammer falls all the way down.  It is almost too complicated a Rube Goldberg arrangement for the average person to learn.  In any case, most of us have played a piano, and we know what it feels like.)

[The diagram above shows the so-called double-escapement mechanism invented by Sébastien Erard, and is an annotated version of an image from Wikimedia Commons.]

Here is a video clip of a key hitting a piece of wire in lieu of a string.  [There are small differences that various piano manufacturers have patented, so this clip may not show what's going on inside your piano, for instance.]



When one plays a piano, one knows that the note keeps sounding as long as you keep pressing on it.  But, obviously, you can't be pressing on the string, because that would damp the sound, and you would simply hear a thud.  What you are pressing against, actually, is just the wooden floor of the keyboard.  It is a clever illusion that has been arranged by the piano engineers that keeps us convinced that our fingers have a direct physical connection to the sound.

In both the piano and the organ, once the key has been pressed, it is the instrument that manages the sound, except that we stop the sound by releasing the key.  All the expression an organist can bring to bear on the note has to be packed into two things: when to press, and when to release.  So in organ music, the fine details of rhythm and phrasing have a lot to do with timing, and an organist chooses the moment at which he or she presses each key with great care.

With a piano, however, there are ingenious devices that enable the player to control the sound.  The velocity with which the key is pressed determines the volume of each note, unlike in the organ, where the volume for the entire instrument has to be set by a pedal.  So when a pianist emotes, and hammers on the keys, he really is making a difference in the sound.  (You can emote at an organ keyboard, but it makes no difference; you can only make it louder by opening up a sort of louvre blind that lets more of the sound through.  Or by adding another stop to your mix.  And only part of the ranks are inside the louvre box (the Swell Box); the rest of the organ is sitting right outside, its volume controllable only by shutting off or turning on ranks of pipes.)

It is this design feature which enables the player to actually affect the volume of each note individually that gave the piano its name: Pianoforte, which means soft-loud.  It's predecessor, an instrument called a fortepiano that was invented around 1750, around the time of Bach's death, had a somewhat simpler mechanism (or action), and was a far smaller and lighter instrument than modern concert grand pianos.  Those old fortepianos had wooden frames on which the (bronze, probably) strings were stretched, and the hammers might have been leather (rather than felt, as they are today).  The bigger, more powerful pianos were developed in the 19th century, and already during the time of Beethoven, there were pianos made with heavy cast-steel frames on which multiple strings could be stretched to high tension.  The higher the tension, the longer the string could be, with a proportional gain in volume, enabling the piano to compete with the larger orchestras of Beethoven's time, and so making piano concertos for large forces possible.  Fortepianos were essentially chamber instruments; indeed Mozart's piano concertos were chamber works, even if the audiences might have numbered a couple of dozen.

Here is Mozart's amazing concerto K 466 in D minor, featuring a fortepiano and a small orchestra.



Here is the same piece played on a modern piano, with modern orchestra:



[Also listen to this version by Gabriella Montero for a less jaunty version. Here is Mitsuko Uchida, a well-known Mozart performer, playing and conducting the same concerto.] 

Modern piano technique, though, is complex; pianists interact with the instrument in complicated ways, and they can convince themselves that caressing the keys in particular ways enables smoother, or more nuanced phrasing of a piece of melody.  The amazing thing is that these techniques actually do influence the phrasing, ultimately via the hammer velocity, the damping, and to a minor degree, even the escapement.  In addition, because of the high tension of the strings, and because the pedals can keep all the dampers off if desired, many amazing effects are possible, via sympathetic vibrations.  A sympathetic vibration is when a second string begins to vibrate, urged by the vibration of a related string; an octave, or some other related note.

To make the point perfectly clear: in playing an organ, once the key is pressed, there is absolutely no point in fussing with the key; you cannot influence the tone any further, except by releasing it.  Furthermore, you cannot influence the note by playing the key hard, or soft.  With a piano, too, you really can't do anything to the key to make a difference to the note, except to release it.  But how hard you hit it (the hammer velocity) does indeed affect the volume.  In addition, experienced pianists exert fine shades of control over the hammer velocity, through sheer experience, and through all sorts of mental devices that may even involve imagining features in the piano that do not exist, but ultimately do affect the tone, through the hammer velocity.

[To be continued, with examples!]

Arch