Was augmented chord used in baroque era?
I don’t think the augmented triad was used on purpose or with much emphasis, at least not in the same way the diminished triad was used. For example, Bach will purposely sustain or emphasize diminished traids and seventh chords, but I wouldn’t expect to hear an augmented triad except as a result of passing tones. You could certainly find the tones C E and G# played at the same time, but usually not in a way that indicates it being treated like a specific chord.
