May was the son of Walter James May, a teacher, and his wife Margaret nee Dodds. He attended Dunolly Public School and won a bursary to East Maitland High School (1896-1898), then transferred to Sydney Boys' High School (1898-1899). He gained a certificate in geology and metallurgy at Sydney Technical College School of Mines and became a metallurgist; but eye trouble led him into a career in music.
Having studied the piano as a child May became organist and choirmaster at St. John's Church of England, Newcastle, and subsequently at the Central Congregational Church in Ipswich, Queensland (1905-1920). He taught the piano and music theory privately and conducted the Esk Musical Union (1907-1910). In 1910 he married Mary Ellen Williams and they had four children. From 1920-1935 he was organist at the Brisbane Tabernacle Baptist Church.
May was a member of the Queensland Music Advisory Board by 1924 and in 1934 became a fulltime lecturer and organiser of Queensland examinations for the Australian Music Examinations Board, a position he held until his retirement in 1952. May organised summer schools in music and speech from 1946 to 1953 and in 1955 was on the Conservatorium Advisory Council, having been a strong advocate for its establishment. He was embittered by the University's lukewarm acknowledgement of his contribution to music in Queensland and in 1963 founded a rival examinations body, the Council of Music and Drama in Queensland.
(Source: G.D. Spearitt, 'May, Sydney Lionel (1882-1968)', Australian Dictionary of Biography, Volume 10, 1986, pp 462-463.)