-Modality: Bb against the C chord just played should be a B natural
-Use of chromaticism: Bb to C to B natural
-F major to F minor: piece modulates to F minor from F major within the same bar, an unusual modulation that suggests modality. This is done again a couple of bars later with a C major to C minor modulation
-Use of diminished 4ths: relates to the baroque idea of expressive use of harmonic devices, therefore use of diminished 4ths is idiomatic of the Baroque era