Of Music and Magnets

I’m finishing a book called “Piano” by James Barron that’s pretty interesting.  The book was a Christmas gift this year because of my recent foray into learning how to play one.  In the book, the construction of a Steinway concert grand piano is followed – from the harvest of the trees that will be formed into it, to the bending and creation of the frame, to the setting of all the myriad of pieces that must be put inside to create a musical instrument from what might otherwise be a large and ungainly piece of furniture.

The book is really fascinating – not in that page-turning “gotta find out what happens” sense – they make a piano — but the book goes into enough history and detail to really give the reader an appreciation for how incredibly complicated these instruments are.

As the book draws to its conclusion, the near-finished piano goes through multiple rounds of tuning and adjustment – for the sound that the piano will produce is the result of many many interdependent characteristics — how are the keys weighted, what is the shape and density of the hammers, what are they covered with, what sort of acceleration do they strike the strings, how much lacquer is used to adjust the sound and in which parts of the scales, how quickly to the hammers descend, how tightly are the pedals adjusted, how do all these sound-producing events interact with the sounding board within the case… its stupefying to me that anyone ever figured this out and the Steinway grands have been essentially unchanged since 1885.  Wow.

The thing that really impressed me is that there are >3400 moving parts in a piano that interdependently cause the sound.  The true skill of a tuner is to find the right way to adjust one thing at a time while keeping everything balanced so that the piano will produce the right sound (frequencies).  That’s quite a skill – and then I realized it reminded me of something that I used to do all the time.

A good chunk of my scientific career has been spent (though not much at all these days) doing Nuclear Magnetic Resonance spectroscopy – or NMR.  NMR is used to decipher the structure and interactions of molecules at the atomic level.  NMR works because atoms are in many ways like tiny gyroscopes and, as it turns out, they align in a big magnetic field.  Now, if those aligned atoms are exposed to an intense radio pulse, they will be knocked out of alignment.  As they recover and come back into equilibrium, they “echo” back information – what sort of atom they are, and in what environment they’re in.  By piecing together the echoes, you can figure out what the molecule is like. An NMR instrument is designed to produce the necessary radio pulses and hear the echoes.  It consists of a large superconducting magnet inside of which lies a very precise radiofrequency transmitter and receiver.

I know I know – what ON EARTH does this have to do with a piano??  Well, a sample is placed in proximity to the radio transmitter-receiver of the instrument, but as it turns out, you need to fine tune the magnetic field to be really really homogenous where the sample is – a tube about 50 mm in height by 5 mm in diameter – not real big.  To adjust the field, the spectroscopist has to “shim” the field — and shimming is the akin to what a piano tuner does.  There are dozens of tiny adjustments that can be made to the field and each of them are interdependent – change x, and suddenly y isn’t quite right.  Go and adjust y and now z is all screwed up and so on (it can be sort of maddening after a while).  The true skill of the NMR spectroscopist is to adjust one thing at a time while keeping everything else balanced to produce the right frequencies (sounds).

Pretty. Damn. Cool.

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7 thoughts on “Of Music and Magnets

  1. Sdede2 said exactly what I was going to say! :) Great post, and sounds like a fasinating book too. Incidentally, I'm currently reading The Sex Lives of Cannibals, to be blogged about soon.

  2. Glad you guys liked it — I wrote it late, so I wasn't sure if it was very coherent… ;) The Piano book is fascinating in a very abstract way b/c you realize just how much time and effort goes into hand-crafting something like that. I'd be curious to see how a "piano" factory produces them differently.
    Oh, and NMR spectrometers are all hand-assembled, too!

  3. WOW! Great article!! I trained with a piano tuner in a former life, but my back was not strong enough. I was just fascinated with the instrument. I learned alot that still comes in handy – if I have a little rattle or sticking key, etc, I can fix it – even a bit of tuning – but I would never attempt to tune an entire piano now – you have to do that almost daily to keep that kind of ear.

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