Electronic musical instrumentsThe ethereal power of the ondes Martenot

IN “The Exterminating Angel”, Thomas Adès’s new opera, a group of people find themselves mysteriously unable to take their leave from a dinner party. Trapped in their genteel surroundings amid the remnants of the soirée, they succumb to claustrophobic puzzlement and, eventually, anarchy. As in Luis Buñuel’s film from 1962, the spell that keeps them captive has no name. But Mr Adès’s opera gives it a voice—an unearthly wail that rings out whenever the dinner guests try to escape their prison.

This siren song is produced by an ondes Martenot, an electronic instrument conceived nearly a century ago by Maurice Martenot. A trained cellist and composer working as a telegraph operator in the French army, he was inspired by the sounds his valve-powered radio equipment made when he scanned the frequencies. It took a decade of development before the first iteration of the instrument that bears his name had its premiere in Paris.

Meaning “Martenot waves”, the ondes Martenot is far from the earliest electronic instrument, yet most that came before were curiosities (like the clavecin électrique, a bell-ringing machine invented by a Jesuit priest in 1759) or highly impractical (it took 30 railroad flatcars to ship Thaddeus Cahill’s 200-ton telharmonium, invented in 1896, from Massachusetts to New York). Martenot’s creation has most in common with the theremin, whose ethereal glissandi are likewise familiar from many a sci-fi score. The two instruments have the same core principle—two radio waves, oscillating at different frequencies, are played concurrently to produce an audible harmonic—and both were unveiled in the late 1920s to a public hungry for the next great invention (the theremin debuted first; the degree to which it influenced Martenot’s designs is hotly disputed). And, at least to begin with, they were played in a similar way: the theremin with a hand wafted before an antenna, the ondes Martenot with a ring drawn along a ribbon.

While the theremin has changed little, the ondes Martenot has transformed beyond recognition. The addition of a keyboard—with keys that can be wiggled to add vibrato—enabled far greater precision. A cluster of buttons like organ-stops allowed the performer to switch between different timbres, from white noise to a crystal-clear sine-wave. By 1950, Martenot had designed three baroque loudspeakers or diffuseurs (one is shaped like a lyre; another is a resonant gong), which aficionados say add unmistakable nuances to the instrument’s sound. 

But this tinkering was a double-edged sword for the instrument’s legacy. The ondes Martenot’s combination of playability and expressiveness have secured it a niche in the canon, while the other musical curiosities of the era—such as the electrochord or the oscilion—have long been forgotten. The instrument remains a remarkably complex device, laborious to manufacture and difficult to maintain.

Cynthia Millar, the ondiste performing in “The Exterminating Angel”, will not be using her original ondes Martenot (one of around 60 estimated to be in existence) at the Royal Opera House, as she did at the opera’s premiere in Salzburg last year. Instead, she will play an ondéa, a near-clone of the instrument designed after Martenot’s death, which boasts an expanded range, improved circuitry and other technical improvements.

Indeed, recent years have seen a proliferation of such ondes Martenot recreation projects, which simplify the more rococo features of the original design. The pressure-sensitive volume button, for instance, now works using electronics, rather than by exerting pressure on a tiny leather pouch containing a secret combination of conductive powders (the recipe is said to include gunpowder). But even these pared-down versions bring problems. “It’s not like I can just ring up and get somebody round to repair it,” says Joshua Semans, a 22-year-old synthesizer enthusiast who owns an ondomo, another kind of ondes replica. “If I took my ondomo into a music shop, they’d say ‘what the hell is this?’” There are a handful of specialist technicians in the world; Mr Semans often carries out simple maintenance himself. 

Yet for all its challenges, the ondes Martenot is sustained by a devoted tribe of fans and a healthy repertoire. Mr Adès—who had never previously written a part for an electronic instrument—is not the first to turn to it to invoke a sense of unworldly power. Arthur Honegger used it in his oratorio about the execution of Joan of Arc, and André Jolivet in his incantatory dances. Olivier Messiaen, who did more than any other composer to ensure its longevity, was enamoured with its versatility and emotional range: he saw it as offering an “extra-terrestrial, enchanted voice”. More recently, it has become a favourite of Jonny Greenwood, the Radiohead guitarist. Many of Martenot’s original valvular creations may be gathering dust, but the surreal voice he first heard on the wartime airwaves will be ringing out for a while to come.