Harty takes further posts in his teenage years as a church organist in Belfast and Bray. While in the latter, he comes under the influence of Michele Esposito, professor of piano at the Royal Irish Academy of Music, who encourages him to pursue a career as a piano accompanist. As Bray is only twelve miles from Dublin, Harty is able go into the city to hear an orchestra for the first time in his life.
After his early career as a church organist in his native Ireland, Harty moves to London
at about age 20, soon becoming a well-known piano accompanist. The Musical Times calls him “the prince of accompanists.” As a composer he writes throughout his career, many of his works being well received, though few are regularly performed in the 21st century.
In his career as a conductor, which begins in 1904, Harty is particularly noted as an interpreter of the music of Hector Berlioz. From 1920 to 1933 he is the chief conductor of The Hallé symphony orchestra in Manchester, which he returns to the high standards and critical acclaim that it had enjoyed under its founder, Charles Hallé. His last permanent post is with the London Symphony Orchestra, but it lasts only two years, from 1932 to 1934, as Harty does not prove to be a box-office draw. According to a historian of the orchestra, Richard Morrison, Harty is “brutally and hurtfully” dropped in 1934.
During his conducting career, Harty makes some recordings with his orchestras. Shortly after his dismissal by the London Symphony Orchestra, Harty begins to suffer the symptoms of a brain tumour. After surgery which includes the removal of his right eye, he resumes his career until 1940, but the tumour returns to cause his death at the age of 61 in Hove on February 19, 1941. He is cremated, and his ashes are interred in the grounds of Hillsborough parish church, near the front door. There is a separate memorial in the church.