22 Sep

New clavichord project

My last clavichord project failed at the last moment, but not through lack of momentum. I got right to the point where I could play a full scale on it, but had to stop there, because I had learned enough from the project to realise that it would not work properly in the end.

The project I had envisioned was a clavichord built from very easily-sourced material: plywood. And the strings were made from high-tensile wire, using only one strand for the higher notes, and two or more for lower-frequency notes.

I didn’t actually expect to get as far as I did. My main intention with this project was to figure out exactly how clavichords work. This was a practice run.

Some mistakes learned from the last project:

  • The key tangent positions are crucial. If they’re off by even the slightest amount, you will miss the string or (even worse) the keys will overlap with each other.
  • When the strings are on, the tension created can warp the clavichord, making it bow in the middle, thus wrecking all your careful measurements and tunings.
  • It’s very hard to find explanations online about how /exactly/ sound-boxes work, such as how to make sure all notes sound equally loud, where to place ribs (if needed), the effects of the various measurements and materials.
  • Tuning is hard.

The new project will address these. I’m planning on building something which will address each of these problems, and also will allow me to test a few things I’m unsure of, and change things easily.

Firstly, the body will not be build as a solid rectangular block, as the last one was.

Instead, it will be built as a lightweight scaffold from metal rods bolted together. This allows me to easily re-arrange it if needed.

To stop the bowing, I will build a truss rod into the base, so if the strings cause the body to bend upwards, I can counter this by tightening the truss rod, pulling it back into shape.

To counter the tangent position problems, each key will be an adjustable three-part lever, which can be bent into shape, then “bolted” once it is correct.

Because the sound-box will probably be the hardest thing to get right, I have the idea of a removable box, so I can experiment with different materials and shapes. To make this possible, the bridge (which connects the strings to the sound-box) will be raise-able in its entirety, so the sound-box can be slipped out under it.

In a traditional “double-strung” clavichord, the string is looped around a tuning peg on the right side (next to the sound-box), pulled across the bridge, across the body, and looped around a pin, then back across the body, across the bridge, and looped to another tuning peg. I don’t really like the design of this, so will be changing it in mine.

In mine, each string will have a “ball end”, like a guitar string. the ball end hooks to the right end of the clavichord, and the string then is stretched over the bridge, across the body, then around a positioning pin and into a machine head. Machine heads are much easier to tune than tuning pins. This method also makes it easier to single-, double- or even triple-string different parts of the clavichord. In pianos, for example, the bass notes are single-strung using very heavy wire, and the treble notes are triple-strung using light wire.

I will also be adding a microphone and jack to mine, so the clavichord can be optionally amplified.

Some even more far-out ideas:

  • Add a touch screen and small computer (Raspberry Pi?) which can be used to display sheet music.
  • This could also be used to display a tuner, such as the awesome DaTuner Pro for Android.
  • And the most difficult: automatic tuning. A robot mechanism for turning the machine heads and picking/tapping the strings automatically to tune to Well-tempered, Pythagorean, Mean-tone, or any other tuning.

Well – that’s the plan! Now to watch some Red Dwarf and forget all about this madness…

2 thoughts on “New clavichord project

  1. Good day and hello
    I enjoy reading your post, and yes it can be frustrating at times,,,
    You should take a look at the frame of a Kurt Sperrhake Clavichord, It is build solid rock, and yet light enought to produce a nice and strong enough sound. I`m rebuilding my 1953 Sperrhake Clavichord and the only problem with it is that its frame is so strong that it takes a little extra time to work around it. The soundbox has a few cracks due to the tension of the blacket. this is the most delicate part, besides the keys being properly aligned.
    I don`t know if the metal rods will produce an strange counter vibration when playing specific notes that aligns with the frequency of vibration of the metal, you should check that. If necessary, cover the metal rod in some kind of plastic shield to prevent that.
    Good luck

  2. Thanks Richard;
    That’s very encouraging! I’m an amateur at best, and was thinking that my ideas were a bit too “out there”, and that the instrument I end up with might not be even called a clavichord.

    I haven’t yet started the new build, still gathering ideas for it, but I think you’re very right about the vibrations. I wonder if maybe they can be countered by simply using plastic washers at the bottom corners of the body; so the main body of the instrument will be “elastic” (for damping), with a solid top frame for the strings and soundbox.

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