Choro is a Brazilian Popular Cultural Manifestation. Its origins date back to the late nineteenth-century trough the encounter of low-middle class instrumentalists at events called “rodas de Choro”. It’s musical practice includes genres such as polka, schottisch, waltz, Brazilian tango, maxixe and choro itself.
These genres differ from each other mainly by rhythmic aspects, whilst share the same formal structure, named by researchers as “rondo form”. This structure has three sections organised in AA BB A CC A, and may be preceded by an Introduction and/or followed by a Coda. Thematically, the sections are usually independent of each other, and the cohesion is maintained by the harmonic relations between each part, which date back to the Classic rondo. Thus, section A is conceived in the main tone of the work, while section B usually contrasts in mode (where it is major becomes minor and vice versa) and section C presents new key signature in a region close to the tonic. Each of these sections usually has 16 bars, symmetrically organised into periods or, more rarely, into sentences.
From extensive analytical research, I discovered works in which this symmetry is not respected. Taking as reference Hepokoski and Darcy (2006), I appropriated the concept of deformation to refer to the compositional resources responsible for the innovations on the formal model considered as a pattern. Thus, I classified the procedures of formal deformation into four large groups: 1) by extension; 2) by abbreviation; 3) by metric impairment; and 4) by the use of mixed meters.