Career and works
Dennehy was born in Dublin, where he read music at Trinity College where he studied composition with Hormoz Farhat. He continued his studies in music at the University of Illinois at Urbana-Champaign (UIUC), with support from a Fulbright Scholarship, and earned his master's and doctoral degrees at UIUC. His post-doctoral musical period included a stint at IRCAM, with Gérard Grisey, and studies in the Netherlands with Louis Andriessen.
In 1997, Dennehy returned to Dublin and subsequently co-founded the Crash Ensemble, which focuses on the performance and recording of contemporary music. His works for the Crash Ensemble include Junk Box Fraud, Derailed, and For Herbert Brun. He later returned to Trinity College Dublin as a lecturer in music. His 2005 work for chorus and orchestra, Hive, displays his developing interest in microtones and harmonies based on harmonic spectra. His composition Grá Agus Bás, which was premiered in February 2007, incorporated music from the sean nós tradition and was a collaboration with the Irish vocalist Iarla Ó Lionáird. He is a member of Aosdána, Ireland's state-sponsored academy of artists.
NMC Records in London released the first portrait CD devoted to his music, Elastic Harmonic (NMC D133), in June 2007. In the spring of 2011, Nonesuch released an album with Grá Agus Bás and the Yeats cycle That the Night Come. His first opera, The Last Hotel, an 80-minute chamber work with a libretto by Enda Walsh about a woman planning her suicide, received its premiere on 8 August 2015 in Edinburgh, followed by performances in Dublin, London, New York and Luxembourg. A recording (taken live from the Luxembourg performances) was issued in 2019. The Hunger, about the Great Irish Famine, premiered in June 2016 at a concert performance in Washington DC, and in a staged production in St. Louis and at the Brooklyn Academy of Music, all with the orchestra Alarm Will Sound.
Dennehy was a visiting scholar at Princeton University from 2012 onwards. He served as composer-in-residence for the Fort Worth Symphony Orchestra in 2013/14. In the fall of 2014, he joined the faculty of the music department at Princeton University.
He wrote Hard Landing about the "Miracle on the Hudson". It was commissioned by the BBC, first performed by the BBC National Orchestra of Wales on 6 February 2025, and had its radio premiere on BBC Radio 3 on 29 March 2025.
