Grade Six Music Theory - Harmony Lesson 3: Inversions
Look at the Bass Note
We know that triads are built using a root, 3rd and 5th.
When we built triads in lesson 2 we always wrote the root as the lowest note (or bass note) of the chord.
However, we can choose another note of the triad to use as the bass note, without changing the basic nature of the triad.
We don't always use the root of the chord as the bass note when harmonizing music, because it tends to sound quite boring after a while.
When a chord's lowest note is not its root, we say the chord is inverted (like, turned upside down).
Let's look at inversions in more detail. We'll use the C major triad, to make things easier.
Root Position
The root of C major is C. When the root is the lowest note in the chord, we say the chord is in root position.
In the Roman numeral system, we write the letter "a" to show a chord is in root position. For example, "Ia" means a tonic chord with the root as the lowest note.
Root position chords are extremely common.
First Inversion
Let's change the order of the notes so that the lowest note, or "bass note" is an E. We are using the third of the triad, instead of the root.
In Roman numerals, we write "b" to show 1st inversion. "Ib" means a tonic chord with the third of the triad in the bass.
First inversion chords are quite common.
Second Inversion
When we put the 5th of the triad as the bass note, we have a second inversion chord.
In Roman numerals, we write "c" to show 2nd inversion. "Ic" means a tonic chord with the 5th of the triad in the bass.
! Second inversion chords are quite rare. We don't normally use 2nd inversions, except in special circumstances, for example, the "cadential 6/4". NEVER use a 2nd inversion chord unless you are sure you know what you're doing.
The Order of the Other Notes
When you're thinking about inversions, the only note you need to worry about is the bass note. It is the bass note which tells you which inversion a chord is in.
Аll the other notes of the chord can be written in whatever order suits them best.
So, for a c major triad in root position we can find: 
In 1st inversion: 
In 2nd inversion: 
Third Inversion
Chords with an added 7th have another possible inversion: 3rd inversion, or "d". Here's G7 (the dominant 7th in the key of C) in its four positions:
You need to be able to recognise third inversion chords at grade 6, but you don't have to write any!
