Why assign numbers to chords?
If you have read part 1 of TTS vol 2 you should know how we use different types of numbers to help us understand about chords and chord sequences. This page gives you a visual explanation/reminder of the relationship between the chord note numbers (arabic numerals) and the function of the chord itself within the key (roman numerals). This sounds a bit more complicated than it really is so we have made this slider to help you visualise what it all means. We have included chord VII, however as explained in the book this is not something you need worry about just yet, but FYI it is called a half diminished or minor 7 b5. This is going to be useful if you want to move on to jazz improvising.
The Chord & Numeral Slider
Chords in the key of C major.
(Click on the menu number to move the slider)
This slider shows you the chords built on each degree of the C major scale, and which notes are in those chords. You can see how we use the numeral system:
- Roman numeral always relate to the tonic note of the key we are in, not the notes of the diffrent chord
- Arabic numerals relate to the root note of each chord.
Three or four note chords
As you know we might have either simple three note chords (AKA triads) or four note chords (AKA 7ths). In the slider the triads are shown with a purple border, the extra note in the four note chords is shown with a blue border.
Answer: if you recall (from reading the book) we make chords by counting up alternate notes from the chord root 1, 3, 5, 7. So the fourth note in the chord is actually the 7th note of the scale
Chord VII is a bit more complicated. I have included it for completeness, but the good news is that at this level we are not going to use it.
But if you really want to know, here is an basic explanation:
As a triad this is called a diminished chord because the interval between the root and 5th is known as a diminished 5th. However the four note version adds a minor 7th and this is either called half-diminished or a minor 7 flat 5.
We use the chord symbol ø7 for half diminished or m7b5 (minor 7 flat 5). Both mean the same thing.
(A full diminished 7th would have a minor 7th that has been flatten by a semitone, called a diminished 7th)