Chord function

Recap: one emerging effect of common chord movement patterns is that locations within the key window start to attract recurring roles, or jobs, or functions. For example, consider one very prominent position on the downward runway, the position just before reaching home. When played as triad, the chord quality is simply major, so in the absence of movement or other information, on hearing that chord you could be in any of three locations in the key window. However, if you play a four-note chord in this position, you get a unique position identifier. To see how this works, consider all of the natural (i.e. thirds-stacked) four note chords in the diatonic scale.

(This is probably seen more clearly in this video)

In this diagram, for the purposes of illustration, so as to pick out the root of each chord visually more clearly, all of these four note chords (called sevenths chords by musicians), are played in first inversion (i.e. the root note is shown more lightly coloured indicating that it is played an octave higher).

This diagram shows the shape of the four note chord based on each root of the diatonic scale (in the key of C for illustration). All three minor chords (based here on D, A and E) have exactly the same shape, known as a minor seventh. But only two major chords have the same shape (here F and C) known by musicians as a major seventh. By contrast the chord based here on G has a unique shape, known as a dominant seventh.

In various forms of music using mainly three note chords, musicians latched onto this idea, using the four-note dominant 7th shape to telegraph to listeners that the harmony was poised above the home position, waiting to fall down to the home position.

This idea applies in any key - there is nothing special here about the key of C. To show this, we can label the notes of the diatonic scale in roman numerals starting from the home position.

This means that chord progressions like II V I (using the above notation) can communicate moving towards home, and are often used as a signature that a section of piece is ending. Such signatures (of which there are many different kinds) are known as cadences. <link to fun cadences>

Borrowing the dominant powered cadence for the mode.
This signature of dominant chord followed by a movement one step down the dominant axis became so useful as an ending signature or cadence, that it soon got borrowed to act as a cadence in the minor mode (i.e. when using the centre minor triad as home as opposed to the central major train as home - even though this chord juts out from the diatonic key window at this point!

If we are using the bottom of the east coast of the white area as the key centre (musicians call this the minor mode), the natural (or musicians would say diatonic) chord above it on the dominant axis should be a minor triad.

However, a dominant chord shape followed by a move down the dominant axis has become so strongly associated with endings that it also works as an ending signal in the minor mode too - even though the dominant chord shape protrudes slightly out of the diatonic key window.

Incidentally in the diagrams above, the A’s are all now circled in red, when previously the C’s were circled. The red circle can be moved to any position in the key window using the mode control panel in the middle on the right.

This is just meant to act as a reminder of the currently chosen home note. In fact this marking is not anything to do with the specific notes C and A - it is the position the key window that is being marked - and the key windows can be moved at any time using the arrows in the top control panel on the right hand side, leaving the notes where they are.

Position of Red note ring - summary

When making music, the red note circle indicate where you want home to be harmonically - but it doesn’t happen automatically. You have to work to make it happen - see establishing keys and modes.

When analysing music, the red note circle indicate where you think the home root is harmonically - though you could be wrong, or it could be ambiguous or other people could interpret it otherwise.

In the trade, we say that the position of the red note ring tells you what mode you are in.

All seven possible positions of the red note ring have historical names. All seven modes can be made to work musically. <see examples>

The mode control panel in the middle of the right hand panel array has buttons laid out to mimic the home note positions of each mode.

The seven buttons are labelled with abbreviation of the seven historical names.

The mode currently in force is named at the top of the left hand control panel.

Using the note label menu, you can label the whole harmony space field with mode names for reference.

Apart from acting as a handy visual marker, selecting a mode causes the roman labelling to start from I at the red circled position (then continue up the diatonic scale from that point).

Home in the Ionian mode

When combined with habitual chord movement on the dominant powered axis, this is known as the major mode

Elements of Harmony

Previous Simple movement games

Next Naming Jumps (intervals)

Home in the Aeolian mode

When V is habitually played as major, this is known as the minor mode

Home in the Dorian mode

The dorian mode has its own characteristic cadential movements <see here>, but can also borrow the modification of V to be played as major for cadences (called the harmonic dorian)