Aaron Cassidy (b. 1976) is a composer, conductor, teacher, record producer, and author. His work as a composer has, for over 20 years, focused on the development of innovative tablature notations that prioritise the physical, bodily, and mechanical aspects of sound-production in music. This approach is perhaps most notable in his work since 2010, which has created a multicoloured graphical notational practice that enables wildly multi-dimensional choreographic actions to be represented in a simple and non-stratified notational space, as well as through a parallel strand of activity since 2015 that has explored new ways of working with what he refers to as ‘non-geometrical’ rhythm, untethering the fundamental rhythmic characteristics of speed and duration from the notational regularity of beats and pulse while still maintaining the functional character and evocative impact of meter and syncopation. His interest in notation has always been driven by an approach to musical material that is deeply physical, resulting in a soundworld that is expressive and energetic, fractured but dancelike, sometimes violently mangled and sometimes fragile and vulnerable, but always grounded in a fascination with the sounds and textures that become possible when we allow ourselves to rethink our assumptions about what might constitute musical material.

This compositional approach has garnered widespread international visibility. His compositions have been presented in hundreds of performances across 27 countries by leading contemporary music specialists, including ELISION, Ensemble Musikfabrik, EXAUDI, Ensemble SurPlus, ensemble recherche, Ictus Ensemble, Talea Ensemble, line upon line, and the Kairos, Diotima, and JACK string quartets. His work has been presented at major international festivals and venues including Donaueschingen, Ultraschall, Warsaw Autumn, Huddersfield, Darmstadt, Gaudeamus, Dark Music Days, Tage für Neue Musik Zürich, Bludenz, Mixtur, Bendigo (BIFEM), Monday Evening Concerts, NYCEMF, June In Buffalo, the ISCM World Music Days, Southbank Centre, Merkin Hall, Miller Theatre, and Sendesaal Bremen, and has been supported through grants and commissions from the Ernst von Siemens Musikstiftung, Südwestrundfunk, the American Music Center, British Council, PRS Foundation, Arts and Humanities Research Council (AHRC), New York Foundation for the Arts, Haupstadtkulturfonds Berlin, the Yvar Mikhashoff Trust for New Music, allerArt Bludenz, RMIT Gallery Sonic Arts Collection, ASCAP, and the London Cultural Olympiad 2012. Recordings of his work are available on 12 commercial CD releases from NEOS, Kairos, NMC, HCR, and New Focus Records.

Also regularly active as a conductor of both contemporary and historical repertoire, Cassidy has appeared with Ensemble Musikfabrik, ELISION, Schola Heidelberg, Ensemble Proton Bern, Ensemble Interface (then as IEMA), International Contemporary Ensemble, and the Northwestern University Contemporary Music Ensemble, leading many dozens of world premieres, including for example new works from Richard Barrett, Mary Bellamy, Ann Cleare, and Erik Oña. From 2008–13 he served as conductor of the Symphony Orchestra and New Music Ensemble at the University of Huddersfield. Notable recent performances include an Ann Cleare portrait concert with Musikfabrik in the Großer Saal of the Berlin Philharmonie for the Berliner Festspiele, recording three works by Turgut Erçetin for the Musikfabrik im WDR series at the WDR Funkhaus, a Swiss tour with Ensemble Proton Bern, and the premiere of Ann Cleare’s opera The Little Lives at the Munich Biennale. He has recorded as a conductor for Kairos and for forthcoming releases on Wergo and HCR.

He has given invited lectures and masterclasses at many of the most significant institutions for new music worldwide, including Harvard, Columbia, Northwestern University, CalArts, SUNY Buffalo, University of Chicago, Oxford, Southampton, Durham, York, RMIT, Monash, University of Queensland, Kunstuniversität Graz, Anton Bruckner Privatuniversität Linz, Hochschule der Künste Bern, Norwegian Academy of Music, National University of Singapore, SEGi College Malaysia, Orpheus Institute Ghent, Goethe Institut-Los Angeles, Kulturstiftung Schloss Wiepersdorf, and the Institute of Contemporary Arts London. His work has been written about and analysed in dozens of books, articles, theses, and dissertations—including in journals such as Perspectives of New Music, Contemporary Music Review, Neue Musik Zeitung, and Tempo—and the work has increasingly been profiled in non-specialist publications as well, most notably in The Atlantic (‘Squiggles are the new quarter notes: why music looks different now’).

As an author his contributions include chapters in the first, second, and sixth volumes of Wolke Verlag’s New Music and Aesthetics in the 21st Century series and journals including Contemporary Music Review, Sonic Ideas/Ideas Sónicas, and Search Journal for New Music and Culture, and and he was the co-editor of the book Noise In And As Music, published in 2013 by Huddersfield University Press, which sold out its first printing in less than three months and has had over 5,000 open access downloads.

He also works regularly as record producer. Over the past 18 years he has produced, edited, and mixed recordings for releases on many of the leading labels in contemporary music, including NMC, Kairos, NEOS, mode, aeon, HCR, and Winter & Winter.

Cassidy has taught at the University of Huddersfield (UK) as Professor of Composition since 2007, and was Director of the university’s Centre for Research in New Music (CeReNeM) from 2017–22. He joined the staff of the Hochschule für Musik, Theater und Medien Hannover in October 2022. He previously served as Lecturer of Composition at Northwestern University in Evanston, Illinois, and as Visiting Assistant Professor of Music at Buffalo State College. He holds a PhD in Composition from the University at Buffalo (SUNY), where he studied principally with David Felder as a recipient of a Presidential Fellowship. Other teachers included Michael Pisaro, Jay Alan Yim, Alan Stout, Marta Ptaszynska, and Pauline Oliveros, in addition to further study with Brian Ferneyhough, Chaya Czernowin, Jonathan Harvey, Richard Barrett, and Alvin Lucier, among others. His conducting teachers have included Stephen Alltop, Erik Oña, Ilan Volkov, Zsolt Nagy, and Peter Eötvös.