It is a privilege to have at my website giselapaterno.com this article written by Juan Rezzuto from WKMT BLOG that clarifies one of the most intricate passages in the Sonata form, the Phrase deviations.
The main topic that this article tackle is the differentiation between the phrase deviations which imply a continuation of the same material that has been exposed, and the interpolation, which implies new and even sometimes, contrasting material with the one existing within the musical phrase. This can be a common mistake among Composition students when they first face a Sonata form, especially by Haydn and Mozart. Both composers are characterized by their irregular phrases and apparent asymmetry due to these resources. Maestro Juan Jose Rezzuto delivers a concise and clear brief from the book "Sonata Form" written by William Caplin.