John Mahon's details are a bit thin although Peter Holman's sleeve-notes are superb, However I decided to consult Prof. Harry White of UCD and Dr Barra Boydell of NUI, Maynooth because they are co-writing an important reference book about Irish composers, A few solutions came up ab initio.
Holman comments on Mahon s lack of lower register being a matter of available instruments is duly supported. Both John Mahon and his brother William were mainly executant musicians working for a living.
John was born in Oxford about 1749 into a quite large Irish family. He became one of the most important clarinettists of the late 18th century in England and Ireland; I quote Dr Boydell. From this we may infer that the Mahon boys worked between England and Ireland as working players on possibly basic instruments.
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 in 1834.