This corpus study constitutes the first quantitative style analysis of Choro, a primarily instrumental music genre that emerged in Brazil in the second half of the 19th century. We evaluate its description in the recent and comprehensive theoretical work A estrutura do Choro (Almada, 2006) by analyzing a set of representative pieces from the Choro Songbook (Chediak, 2009, 2011a,b), a central reference for this genre. We digitized this resource by transcribing the chord symbols and formal structure of all 295 pieces, and publish it as the freely available Choro Songbook Corpus. Our approach uncovers central stylistic traits of this musical idiom on empirical grounds. It thus advances data-driven musical style analysis by studying both harmony and form in a musical genre that lies outside the traditional canon.