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On the right is a loudspeaker, on the left is a gong. What?

Normally we expect a loudspeaker to look like a loudspeaker, but back in the 1920s things were not so set in stone. Perhaps a return to old-school creativity is due?


I was privileged last night to attend a performance of Turangalîla by Olivier Messiaen, first performed in 1949 to highly critical reviews, but now considered a show stopper in the world of orchestral music.

I won't bother you with too many details, which you can find here, here and here, because I want to get on to the fun stuff that I teased in the title of this article. But it's worth saying that the work features a large orchestra, plus a piano, plus a celeste, plus a keyboard glockenspiel, plus...

...an ondes Martenot, named for its inventor Maurice Martenot. It looks like this...

Ondes Martenot

Yes, it's a keyboard instrument. Some might say it is a early synthesizer, but its sound source is a simple oscillator that doesn't begin to cover the vast range of sounds that are now possible through synthesis.

But that simple oscillator... Well think of the simple strings of an electric guitar. They don't make much of a sound when played unplugged. But connect the guitar to a pedalboard, amplifier and speaker cabinet, then we have a whole universe of sound from Les Paul to Dave Gilmour to Buckethead and more.

So in the ondes Martenot (French for Martenot waves) the oscillator is amplified and connected to loudspeakers, but these are not normal loudspeakers - they are purposely designed to alter the sound, which is not the way we think of loudspeakers (other than in electric guitar cabinets) today when we strive more and more for accuracy.

When, where, how?

Going back to Turangalila, the performance I attended was one of the BBC Proms, which is a festival of promenade concerts in the Royal Albert Hall in London, held annually. The orchestra was the BBC Symphony Orchestra, conductor Sakari Oramo, with pianist Angela Hewitt and ondes Martenot performer Cynthia Millar.

The performance was as brilliant and exciting as I expected it to be. You can sample one of the most popular parts of Turangalila in an old but powerful-sounding performance here. The ondes Martenot player, either by some strange coincidence or because there aren't many of them around, is again Cynthia Millar.

After the BBC Proms performance during the applause, the thought came to mind that I might rush to the front as soon as I could and take a few photos, which as you can see I did just that - unfortunately with my old and rusty iPhone 5, but they're good enough to show some interesting details.

After I had taken a few shots and the audience had mostly dispersed, I noticed a small crowd gathering around me, which justified my reasoning for getting to the front first. And then...

Cynthia Millar with the ondes Martenot

Cynthia Millar came on stage, presumably to dismantle her instrument. We gave her a small but warm round of applause. And then the questions started coming. Everyone wanted to know more about the ondes Martenot, and Cynthia was fantastic in giving us answers in detail and explaining the different loudspeakers. Of course as someone interested in all aspects of sound production I knew most of this already. But that was only from book-learning. To hear it from a performer brings the whole thing so much more alive. And so to the loudspeakers (you can learn more about the keyboard itself here)...


The loudspeaker on the right in my main image is called the Palme, which I am informed is because of its shape like the leaf of a palm tree. Sound is produced by the motor part of a normal moving coil loudspeaker drive unit, but instead of connecting to a diaphragm, it excites the bridge of the instrument and thence the strings. Additional resonance is provided by the hollow body, like that of an acoustic guitar.

Ondes Martenot Palme loudspeaker

Ondes Martenot Palme loudspeaker

In case you're wondering, yes the strings are tuned. And there are more strings round the back.

The sound of the palme is quiet and delicate, and totally unlike any other instrument. Here's an example, just ten or twelve seconds before the topic changes, but it should give a good indication.


Take a look at this...

Ondes Martenot Métallique loudspeaker

From the front this looks like a normal loudspeaker cabinet. But then Cynthia turned it round. As you can see, there is no conventional loudspeaker diaphragm inside. Instead the moving coil motor is attached to a small gong. The idea is again not to reproduce the signal from the oscillator precisely, but add rich harmonics that create a much more interesting sound.


I don't have such a good picture of the third loudspeaker, but in any case there doesn't seem much to see...

Ondes Martenot Résonance loudspeaker

But no, it's not just an ordinary loudspeaker, inside a moving coil motor drives springs into vibration, thus creating yet another harmonic texture that is available to the player. I imagine that if I got the chance to look inside, I would see something quite like a spring reverb unit, but made so that it transfers vibrations in the spring into the air with reasonably high efficiency.

My thoughts...

Why don't we have more loudspeakers like these?

It seems to me that these ideas dating back to the 1920s have not been given the attention and further development they deserve. There are more ways to create sound through electro-acoustic means than the conventional moving coil drive unit, designed to transform an electronic signal as accurately as possible into real sound in air.

Yes we have stomp boxes that alter a signal electronically; plug-ins that alter a signal digitally. But what about loudspeakers that alter a sound electro-acoustically. (And what about loudspeaker modifiers that alter a sound after it has been produced by a loudspeaker, and purely acoustically? - Actually we cover that in one of our Audio Masterclass courses, with some fascinating results from our inventive students.)

I suspect there may be great adventures ahead. But in the meantime, here's more of Cynthia Millar and her ondes Martenot. Enjoy...

P.S. (Moan and groan department) Whenever the ondes Martenot or Theremin are heard or mentioned, someone is bound to say that they sound science-fictiony (yes, someone did last night). In fact, it isn't that these instruments sound like science fiction, it is that what we expect science fiction music to be like sounds like these instruments. The ondes Martenot and Theremin are capable of a huge range of expression and can fully take their part in music of all genres.

By David Mellor Thursday July 19, 2018
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