John was born in Oxford about 1748 into a quite large Irish family. He became one of the most important clarinettists of the late 18th century in England and Ireland. Mahon made his debut in 1772 as a performer and moved to London for a while. He made frequent trips to Dublin but this did not stop him playing at the Three Choirs Festival from 1773 to 1811. He was also a fixture at the Birmingham Festivals 1788-1823. He married in Dublin in his thirties and spent some time in Co Cork. In 1825 he finally retired to Dublin and died at the great age of 85.
