Ricketts joined the Royal Irish Regiment in 1895. He was enlisted as a Band Boy. He was a good cornet player and was put into the regimental band. The band went with the regiment to Limerick in Ireland, and then to India. In his free time, Ricketts learned all the other band instruments. When he was 15 years old, he wrote his first piece, which was called "For Service Overseas". It has never been published. In 1903, he was recommended for entry into the Student Bandmaster Course at the Royal Military School of Music, in Twickenham, Middlesex. Musicians who were as young as Ricketts were not nominated very often, but Ricketts was very skilled.