“Professor” Joe O’Leary (1897–1977), born in Maine, was a fiddle player, bandleader, and entrepreneur whose career reflects the evolving landscape of Irish-American music in the early twentieth century. His family relocated to South Boston in the early 1910s and by 1919 he was a prominent bandleader, directing an ensemble that provided Irish and American repertoire for social events. In the early 1920s, O’Leary’s interest in the revival of traditional music intensified and c.1923 he founded the Celtic Harmony Club, an organization dedicated to Irish music and dance. By 1925, the club included leading figures such as pianist/bandleader Dan J. Sullivan and button accordionist Jerry O’Brien. O’Leary further expanded his reach in late 1926 with a syndicated radio program which led to the establishment of O’Leary’s Irish Minstrels, his group that recorded 45 sides for Columbia Records and prior to World War II they achieved considerable success. His band’s distinctive sound, notably incorporating a brass section, anticipated developments in Irish-American dance band music in Boston, including the work of later figures such as Johnny Powell. His friendship with Justus O’Byrne Dewitt was instrumental in DeWitt’s early success in Boston.