19 February 2016

The Impossible Clavichord

The following is a first draft for an introduction to program notes for an informal recital I plan to do sometime in the future, featuring some well known works of Bach and a rarely heard, but quite lovely, little suite by his favorite pupil, Maynard G. Krebs. I mean Johann Ludwig Krebs. Who invented the Krebs cycle. Oh well. ​(Just trying to counter the essay's rather too serious tone). If this kinda thing doesn't interest you, by all means, click delete forthwith.


It's likely that most of you have never even seen a clavichord close up, and most people, even if disposed favorably towards "classical music," are a little unclear, if they know at all, on the difference between a clavichord and a harpsichord. So here's a quick primer. The clavichord, which has antecedents dating back to antiquity, is a very simple instrument. It consists of a resonant soundboard, a box with a stiff block with pins in it to hold the strings under tension, a bridge with pins in it to stop the strings at a certain resonant length to make a tuned note, and a set of keys with little flat brass strips of metal called tangents embedded in them. These, when they are levered up so that the tangents strike the stings, both stop the strings… i.e., give them their sounding length that determines their pitch, and impart the actual energy to the strings to produce the sound. There can be no simpler keyboard instrument.

Well made Clavichords have a lovely, sweet sound, and, like the later pianoforte and unlike the harpsichord, they are capable of dynamics… if you strike the string harder (faster, actually)​, the sound is louder. Music of exquisite expressiveness is possible on the clavichord. Harpsichords, the earliest versions of which date from approximately 1450, entail a mechanism whereby the string is plucked by a complicated mechanism with a plectrum embedded in a moving piece called a jack. They cannot vary the volume of the sound, although they are capable of articulation, meaning whether the notes are connected together in time, or more separated (legato vs. staccato).

The problem with clavichords was always that, while they are capable of dynamics, the range is meager, to say the least. From pianissimo to piano. The earlier single-strung instruments, in particular, were not loud enough to accompany a singer or string instrument, or even be clearly heard, alone, in a big room, still less any kind of hall. Later, larger instruments were made, but they aren't significantly louder, because there are physical limits to the sound the simple lever mechanism can produce.

It's generally assumed that the impetus for Bartolomeo Cristofori, in the early years of the 18th century, to develop the first fortepiano, the ancestor of the modern piano, was to create an instrument with the harpsichord's volume and the clavichord's ability to play loud and soft (hence the name). This theory is actually rather dubious, as clavichords were not particularly popular in Italy at the time, but it makes a good story. In any case the lack of dynamic expressiveness of the harpsichord was always recognized as a deficiency. Still, as with any kind of limits, it also represented an opportunity for the creative use of the instrument in ways in which this lack of dynamics did not matter. In fact, much of the instrumental style of the so-called High Baroque can be associated with the style of music that harpsichord composition gave rise to.

Certain composers, notably Bach, his son C.P.E. Bach, and their predecessors Johann Kuhnau and J. J. Froberger, are particularly associated with the clavichord and its more subtle capabilities. The instrument has long had its champions, for its sweet sound, and its delicate and nuanced expressiveness. Some music, such as Froberger's suites and Bach's French Suites and the Well-Tempered Clavier, seems particularly to have been written for the clavichord. I believe, from stylistic considerations, that some of the keyboard music of Bach's favorite pupil, Johann Ludwig Krebs, was also clearly written with the clavichord in mind.

The Pianoteq keyboard modeling software I am using contains a modeled clavichord, based on a German copy, made in 1941 by the Neupert firm (noted for its rather clunky harpsichords). Note that the date indicates that this instrument was made during the depths of the Nazi regime, but I guess that just shows that music persists despite everything. Anyway, this instrument is a "C.P.E. Bach" style clavichord, in other words, similar to the largest, 61-key double strung clavichords ever built, from around 1740. The instrument has a clear sound, but the actual physical instrument still lacks volume, and it also has a certain deadness of tone, resulting from pushing the physical limits of the instrument to ​an extreme.

But the software, because it is ​digitally ​modeled rather than sampled, allows the user to tweak various parameters. It's possible to increase the "string length" parameter from the actual instrument's 0.6 meters or so to 2½ meters (or more, but if you go too far it starts to sound rather artificial). This decreases the "inharmonicity," making the sound purer and less "tinkly." You can also increase the soundboard resonance, to give the sound a rounder, fuller quality. You can amplify the volume of the sound, across the board. Obviously, none of these things is possible with a real instrument. The real soundboard is made from spruce. No real soundboard can be magically made half again as resonant. If you made the strings 2½ meters long, the case that would hold their tension would be heavy enough to deaden the sound overall, and the brass strings would break before you could tune them to the correct pitch. The sound the instrument produced with such long strings, even if they could exist, would be so weak it would be almost inaudible. Hence, the wonders of technology: a recognizable, even idealized, clavichord sound, sweet, expressive, reasonably loud, and absolutely impossible in an real acoustic instrument.

I have tweaked the Clavichord model on the software in just this way, to produce a playable but physically impossible instrument, that I believe makes a very nice vehicle for playing music by composers such as the great Bach and his star pupil, Krebs; music which was almost certainly written with the clavichord in mind. (Although it can be, and often is, played on the harpsichord, modern piano, or sometimes even organ).

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