Following compulsory military service and completing his studies at college, Davis served as a clarinettist in the band of the Life Guards. Stationed at Windsor, he had continual opportunities to attend concerts in London under conductors including Sir Thomas Beecham and Bruno Walter. In 1949, he began his career as a freelance musician (the "freelance wilderness", in his own phrase) where he remained until 1957. His first conducting work was with the Kalmar Orchestra, which he co-founded with other former students of the Royal College. He was subsequently invited to conduct the recently founded Chelsea Opera Group in "Don Giovanni". In the early years of his career, he also took some engagements as an orchestral clarinettist. What seemed at first to be a full-time conducting appointment, for the Original Ballet Russe in 1952, ended abruptly after three months, when the company collapsed. In between sparse conducting engagements, Davis worked as a coach and lecturer, including spells at the Cambridge University Musical Society and the Bryanston Summer School, where a performance of "L'enfance du Christ" awakened his love of Berlioz's music.