Light-Beam Piano

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Ah, such elegance!  A consummate pianist playing her fingers over the keyboard as beams of light flash through spinning disks to produce sweet music through honking great horns that look as if they've been nicked off a steamship.  It's a pity that Herr E. Welte's of Germany's 1936 Light-Tone or Light-Beam Piano never became a mainstay of the classical music scene.  It's such a monster of an instrument that I'd go to a concert just for the curiosity value.  Hook this baby up with a couple of kettle drums and a Chinese gong and it would carry all before it at any Battle of the Bands.

The speaking clock.

The principle behind the light-beam piano is rather interesting and up until 1963 you could have found a perfect example of it anywhere in Britain just by ringing up the Speaking Clock.

When I first heard the Speaking Clock as a boy I thought that it must have been the most thankless job on the face of the Earth.  I imagined that there was some woman with a voice box like leather stuck in an office day and night reading off the time.  Maybe, I thought, they gave her time off, but I couldn't see how.  I could never even detect when she got a chance to take a sip of water, much less get her head down for some sleep.  Later on, someone in a fit of exasperation explained to me that the Speaking Clock was, in fact, a recording.  That made sense, except that I still could not imagine how anyone could have the stamina to manage to read out the time even for a record at ten second intervals to fill up twelve hours worth of time signals.   Besides, how do you make sure the pips sound in the right place?  What happens if the record wears out, as it was sure to do?

The Speaking ClockIt turns out that the lads at the GPO used the same dodge that made the light-beam piano tinkle out notes.  The Speaking Clock, in fact, consisted of four motorised glass disks with a beam of light shining through each one.  One disk had a recording of the woman reading out the hours, the second had her reading out the minutes, the third the seconds, and the fourth had the pips. 

That saved a lot of recording of a lot of very dull lines about "Ten twenty-one and 30 seconds" and all that.  Just read read out the hours, then the minutes, then the ten-second intervals and you're laughing.

A Speaking Clock disk.But why glass disks?  And what has that to do with pianos?

Sound film (arrow indicates soundtrack).That's where the clever bit comes in.  If you take a magnifying glass and look at a piece of sound motion picture film you'll see a squiggly line running down one side between the picture and the sprocket holes.  This is the soundtrack of the film.  The sound is recorded and printed on to the film as this line, much as sound is recorded on a phonograph record as a squiggly line cut into the vinyl.  And if you don't know what a phonograph record is, I shall hit you with my cane.  As the film runs, a light shines through the strip on to a photoelectric cell and turns the squiggles back into sound.

The glass disks  of the Speaking Clock and the light-beam piano do exactly the same thing.  On the Speaking Clock the woman's recorded voice is printed the same as is the soundtrack of a motion picture, but on the light-beam piano, it is musical tones that are printed so that when the pianist strikes a key a light shines through a track and produces the desired tone.

In this close up of one of the light-beam piano disks you can see the tone tracks.  One thing you may have noticed is that the tracks don't look like the sort of continuous, irregular squiggles that you see on a film soundtrack.  Instead, you'll see that they are quite regular, even geometric in shape.  That is because the tone tracks for the light-beam piano aren't made by recording real sounds, but by etching the shapes directly on to the disks so that the piano maker can get exactly the tone he wants.   Call it custom-tailored sound to order.

At the end of the day, though it's all terribly technical and complicated and you have to plug it into the mains to get it to work anyway, so maybe it's best to just stick with the banjo.

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