Diatonic Chords and the Major Harmonic System
When music is in one specific key, it will typically use a set of chords based on the diatonic scale of that key. Triads are built on each pitch of the diatonic scale, creating what is called the harmonic system.
Using the E flat major scale that was covered in the section on melody, we can create a group of triads that are used in music that is in that key. Follow each of these steps to figure out the diatonic chords.
1. Write the E flat major scale on the staff.
2. Create a triad for each of the notes of the scale by writing the 3rd and 5th scale degrees above each pitch.
3. Write in the rest of the appropriate accidentals to create the diatonic chords in E flat major. E flat major has three flats: B flat, E flat, and A flat. Write a flat sign in front of every pitch that is a B, E, or A.
4. Each one of these chords is either major, minor, or diminished. The chords are identified with Roman numerals. Major chords use capital Roman numerals while minor and diminished chords use lower case Roman numerals. Diminished chords are indicated with a small circle symbol, as shown below for the chord based on the seventh scale degree. In the example below, the name of each chord is printed above the staff, and the appropriate Roman numeral is printed below the staff.