Exoplanets, a cosmic tone poem for orchestra, was written for the London Philharmonic Orchestra and the Basel Symphony Orchestra. It was commissioned by the London Philharmonic Orchestra, as part of their 25/26 season, and Basel Interfinity Festival *. It was premiered on November 29th, 2025, at the Royal Festival Hall, conducted by Edward Gardner. It received its Swiss premiere on March 19, 2026, at the Basel Messehalle, conducted by Lin Liao.

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* In collaboration with Professor Raymond Pierrehumbert, Associate Professor Hannah Wakeford and NCCR PlanetS (Switzerland)

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Programme Note (full version)

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An exoplanet is a planet outside of our solar system. Once only theorised, scientists have now discovered over 5000 of these alien planets with telescopes like the James Webb Space Telescope. They are strange, beautiful and wild beyond anything we might have dreamed of ourselves. This piece, Exoplanets, is a cosmic tone poem - I wrote it to sound like it is not of this Earth.

 

Every exoplanet researcher builds on what others learn - nobody works in isolation. Similarly, Exoplanets is a continuous melting pot of ideas, not a set of distinct movements. Different “worlds” emerge, disappear, and reappear changed by what has occurred in the meantime. There are worlds with skies dominated by thousand-mile-an-hour clouds of glass and ocean worlds where boundaries between liquid and gas are blurred. There are worlds that wander between stars in total, frozen, darkness and worlds where, if you were to stand on their surface, you would experience an infinite, radiant, sunrise.

 

I can’t help but imagine what I called “exomusic” - alien music. Would their rhythms correspond to what they see in the night sky, and would their voice be adapted to carry sound in “air” very different to our own? On the Voyager spacecraft, we sent Bach to outer space - would an exocivilisation recognise anything about it?

 

Just as inspiring are the methods we use to discover exoplanets. We learn so much from so little. The slight wobble of a star, pulled by gravity, tells us there is an exoplanet lurking unseen. A tiny change in starlight tells us what an exoplanet’s atmosphere is made from. This piece aims to capture that attention to detail. Harmonies and melodies wobble and drift, timbres are filtered, absorbed, re-emitted like light.

 

Telescopes tell us everything we know about exoplanets. Telescopes are time machines. They reveal the universe as it was, and scientists use them to predict the future of our planet. We see planets with strange atmospheres and runaway greenhouse effects; perhaps that can help us model climate change on Earth. What we don’t see is any other life. We seem to be utterly alone in both space and time. Are we so unique? Or is it that any life flourishes only for an infinitesimal moment in the unfathomably long life of the universe - a moment we can’t find in our time machines. These exoplanet-oracles have an aura of inevitability about them. In 500 million years, the warming sun will prevent photosynthesis, eradicating almost all life, and in 5 billion years its expansion will destroy Earth entirely. There will be no trace of us for future exocivilisations to see. They, also, will seem to be utterly alone. This was always in the back of my mind when composing Exoplanets.

 

Spoiler warning: if you prefer to imagine your own stories about what you’re hearing, I encourage you to stop reading now, as I am going to reveal some specific scientific inspirations.

 

Raymond Pierrehumbert’s work on hydrogen-ocean (Hycean) worlds was the original inspiration for this work. Hycean exoplanets have a liquid ocean and hydrogen-rich atmosphere. Unlike on Earth, there is no clear distinction between the atmosphere and the ocean; the world moves seamlessly from gas to liquid. If you were falling, you’d drown before you splashed. Exoplanets begins with percussion instruments submerging into water, and the first few minutes explore that sense of liminality, testing where one type of sound transforms into another, trying to blur those boundaries. Ray also studies the runaway greenhouse effect on these worlds - heat cannot escape the exoplanet, instead boiling the ocean, creating a more hydrogen-rich atmosphere, trapping even more heat. This exponential growth is also audible in the early minutes of Exoplanets - once an instrument enters the texture, it does not escape.

 

Ray put me onto the idea of orbital resonances, which is when notes are tuned according to how quickly exoplanets orbit round their star. My collaborators at the Swiss PlanetS research centre pointed me towards the TOI-178 system they discovered with their CHEOPS telescope, which has an unusually perfect set of orbital ratios. These ratios create a 6-note musical motif, which is outlined at the very beginning of the work in tuned percussion, and returns many times in different forms. A ratio can also be used to create a rhythm, if you explore it horizontally (in time) rather than vertically (in harmony). The CHEOPS ratios underpin the complex and alien percussion rhythms that follow the Hycean music, and I also use it to create harmonies that exist outside of Western tuning systems. I spoke with several collaborators about “technosignatures” at various points - signals that could only be explained by intelligent life (we haven’t found any yet). Technosignatures would probably repeat inorganically, which informed a lot of Exoplanets’ repeated materials.

 

WASP-17b is a “hot Jupiter” - it’s a gas giant like Jupiter and orbits very close to its star. My collaborator Hannah Wakeford published some incredible research showing that WASP-17b has clouds of quartz, which is an extremely beautiful image. It is also tidally-locked, meaning one extremely hot side is always facing its star and one very cold side is always facing away. This enormous energy gradient, combined with the quartz cloud imagery, gave rise to the section of the piece which alternates between extremely slow and extremely fast playing in the orchestra.

 

I want to thank each of these scientists, and the many researchers in their labs, for their generosity in explaining their research to me and why it matters.