The remarkable story of how modern Irish music was shaped and spread through the brash efforts of a Chicago police chief. Irish music as we know it today was invented not only in the cobbled lanes of Dublin or the green fields of County Kerry but in the burgeoning American metropolis of early-twentieth-century Chicago. The boundaries of the genre combine a long vernacular tradition with one man's curatorial quirks. That man was Francis O'Neill: a larger-than-life Chicago police chief, and an Irish immigrant with an intense interest in his home country's music. Michael O'Malley's The Beat Cop tells the story of this hardly unknown yet little-investigated figure, from his birth in Ireland in 1865 to a rough-and-tumble early life in the United States. By 1901, O'Neill had worked his way up to become Chicago's chief of police, where he developed new methods of tracking people and recording their identities. At the same, he also obsessively tracked and recorded the music he heard from local Irish immigrants, favoring specific rural forms and enforcing a strict view of what he felt was and wasn't authentic. His police work and his musical work were flip sides of the same coin: as a music collector, O'Neill tracked down fugitive tunes, established their backstories, and formally organized them by type. O'Malley delves deep into how O'Neill harnessed his policing skills and connections to publish classic songbooks still widely used today, becoming the foremost shaper of how Americans see, and hear, the music of Ireland.