Inversions

An inversion is the same chord with a different chord tone as its lowest note. A C major triad is C E G. Whether you play C E G, E G C or G C E, it is still C major. The pitch classes never change. What changes is the bass note, the note your ear hears as the floor of the chord.

Play the three versions in a row. Same chord, three different characters: solid, then lighter, then floating. A triad has three notes, so it has exactly three positions: root position plus two inversions.

Root position means the root, the note the chord is named after, is in the bass. This is the way you first learned every triad, and it is what a plain chord symbol like C or Am means unless told otherwise.

Root position is the most stable sound a chord can make. The bass and the chord name agree, so the ear has no doubt about what it is hearing. That is why songs usually begin and end in root position: it plants a flag.

First inversion puts the third of the chord in the bass. Take the root off the bottom of C E G and move it up an octave: E G C. Degree 3 is now the floor, degree 1 is on top.

First inversion sounds lighter and more mobile than root position. Because the third is the note that carries the major/minor colour, putting it in the bass makes the chord feel warm but less final. That makes it perfect for the middle of a phrase, where you want to keep moving.

Second inversion puts the fifth of the chord in the bass. Invert once more, moving the E from the bottom of E G C to the top, and you get G C E. Degree 5 is the floor now.

Second inversion is the least stable of the three. With the fifth underneath, the chord feels like it is leaning on something and wants to move. The ear half-expects the bass note to become the root of the next chord. Composers use exactly that pull before a cadence, as we will hear in section 11.

Inversions are written with a slash: the chord name, a slash, then the bass note. C/E is read "C over E", a C major chord with E on the bottom. The part before the slash tells you *which notes*; the part after tells you *which one is lowest*.

Slash notation is what you will see on lead sheets, in songbooks and in the Harmony Spiral composer. It is the notation we use for the rest of this chapter.

The bass note colours the whole chord, even when everything above it stays the same. To hear this clearly, keep the upper notes fixed, E G C in the middle of the keyboard, and change only the bass underneath.

Play the three and try to say the position before you read the label. A quick test for your ear: the root-position chord is the one you could comfortably end a song on. The other two sound like a comma, not a full stop.

Inversions work on every triad, not just major ones. The rule is the same: put degree 3 in the bass for first inversion, degree 5 for second. Only the formula of the chord changes.

The diminished triad is interesting: Bdim/D puts the bass on D, and the chord starts to sound like a spicy version of a G chord. In fact it shares two notes with G7. First-inversion diminished chords are the form composers use most, because the bass moves by step while the harmony keeps its bite.

The number one reason to use inversions is the bass line. In root position the bass jumps from root to root; with inversions you can make it walk by step through the scale while the chords stay exactly the same.

Only two chords are really changing here: C, then F, then G. But by inserting C/E and F/A the bass climbs C E F A G instead of leaping C F G. Play the progression chord by chord, then play the bass notes alone to hear the line the inversions created.

Voice leading is how each note of one chord travels to a note of the next. The smoothest rule is simple: keep the notes the two chords share, and move the rest by the smallest step. Inversions are what make that possible without changing the harmony.

Take C → Am. The two chords share C and E. If you play Am in root position after C, all three notes jump: C E G → A C E. But hold the C and E where they are and move only the G up one step to A: C E G → C E A. That is Am/C, first inversion, and it fell out of good voice leading by itself.

The same logic gives C → F/C (keep C, move E to F and G to A) and C → G/B (keep G, move C to B and E to D). Notice how often the smooth answer is an inversion. Play each pair both ways and listen for the difference between three voices leaping and one voice sliding.

A pedal tone is a bass note that stays put while the chords above it change. It is inversions used the other way round: instead of choosing the bass to make a line, you hold the bass and let the harmony move over it.

F/C is simply F in second inversion. G/C is different: C is not a note of G major, so it is not an inversion at all. It is a true slash chord, a G triad sitting on a foreign bass. It sounds tense, and that tension releases the moment the bass is confirmed as the root of C.

Pedal tones create a feeling of stability with movement: the ground never shifts, but the colours above it do. They are common at the start of a song (to establish the key) and at the end (to hold the home note while the harmony says goodbye).

Two progressions show what inversions can do better than any explanation. The first is the descending bass line of the Pachelbel Canon; the second is the cadential second inversion, the most famous use of C/G.

Everything in this chapter came from one fact: a triad has three notes, so it has three positions. The next chapter adds a fourth note to the chord, and a chord with four notes has four positions: root position plus three inversions.

The third inversion, with the seventh in the bass, is a new sound: the bass itself is the note that has to resolve down. G7/F → C/E gives a bass line F to E over a perfect cadence. Keep the habit you built here: watch the bass, keep the common tones, and let the inversions do the walking.