Hardebeck was born of a German father and a Welsh mother and came to live in Ireland in 1893. He was an organist and teacher in Belfast and won several composition prizes at the Dublin Feis Ceoil. Belfast’s Bloody Sunday of 1913, World War I, and the Irish Civil War contributed to making him an ardent Irish nationalist, who coined the sentence, ‘I believe in God, Beethoven and Patrick Pearse’. In 1922 he was the first professor of Irish music at University College Cork, but returned to Belfast in the following year. He lived in Dublin from 1932 arranging Irish traditional music for various instrumental and choral forces (many for educational purposes) for An Gúm, the government publisher of the Republic of Ireland.
Hardebeck was the first classically-trained composer to acknowledge the irregular metre of Irish traditional music in his art music arrangements, which consequently abound with frequent bar changes throughout the music. He made very influential arrangements e.g. of Úna Bhán for voice and piano, many published as early as 1908.