Keys are show in yellow using letters. The letter alone indicates a major key, if followed by an m, a minor key. In the example we show the C major, B flat major and A minor keys.
Roman numerals in lowercase correspond to degrees with minor triads
Degrees with diminished triads
Triads in first inversion
Triads in second inversion
Sevent chords in root position
Seventh chord in first inversion
Seventh chord in second inversion
Seventh chord in third inversion
Dominanth ninth chord
Minor dominanth ninth chord
Dominant ninth chord in first inversion
Secondary dominant and diminished sevent chords
Neapolitan sixth chord
Italian augmented chord
German augmented chord
A first degree seventh chord in first inversion with an augmented fifth
Diminished sevent chord with a common note to the dominant chord to which it resolves. This chord has no standard name in traditional harmony and theorist rarely talk about it although it is very common. Walter Piston calls it a II degree seventh chord with raised root and third. We use the term appoggiatura diminished seventh. We could also use the term common note diminished seventh.
Example from the Sonata: