Diatonic chords in any major key can be labelled as I – ii – iii – IV – V – vi – viiº, where upper case Roman numerals denote major chords and lower-case numerals denote minor chords.

Diatonic means that the chords are made ... We use uppercase numerals to denote major chords, and lowercase for minor and diminished chords (there’s always one diminished chord - the vii chord ...

Haydn’s Symphony No. 101 in D major, ‘The Clock’, is in a major key and uses mainly diatonic chords: A dominant seventh ... subdominant and relative minor keys are all fairly common in ...