He received a BSc in applied mathematics from the University of Limerick in 1985 and supported his early compositional activities with a day job as a statistician and technology analyst.

[1] He is known for his narrative cantatas – works he has written for orchestra and choir based on Irish mythology – and for the aria ‘Vide Cor Meum’ originally composed for the film Hannibal, directed by Ridley Scott and starring Anthony Hopkins.

[2][3] The Children of Lir, released in September 1993, remained at number one in the Irish classical charts for a full year.

[6] Cassidy now divides his time between Los Angeles and Ireland, where in addition to his concert work he has scored films and documentaries.

He is a relative of the singer Sibéal Ní Chasaide[7] who sang his composition Mise Eire at the official government commemorations of the 1916 Rising.