Interpretation
When a composer has not directly indicated a major or minor chord to be played it is occasionally acceptable to add Picardy thirds to a work in the interests of variety, especially in earlier music. This would usually be a decision made by the continuo players in a chamber work. For example, in performances of the "Rosary" Violin Sonatas by Heinrich Ignaz Biber, many continuo players add variety to the frequent repetitions in movements consisting of variations by adding the occasional Picardy third. However, over-indulgence of this liberty could weaken the work's structure.
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