How Roman Numerals Are Used in Music
1. Scale Degrees
Roman Numerals are often used within music as a way of understanding chords. You most often see them in classical music analysis or in music theory books as a means of understanding chords.
But…there is a little bit more to the Roman Numerals that we use than you may think.
So firstly, what are Roman Numerals used for?
Well…Roman Numerals are used to tell us which chord is being used in a piece of music from a particular scale.
Let’s say we are reading a piece of music in the key of C major. A C major scale contains the notes C, D, E, F, G, A and B. In order to form standard triad chords from this scale we can play alternate notes. This means that a C chord would be the notes C, E and G and this would be chord 1 (Chord I) from the scale. Chord 2 (Chord ii) would be a D chord and that would be the notes D, F and A.
Often in a piece of music you may come across a situation where the piece of music is modulating to a different key and therefore starting to use a different scale. In this situation you may have a “pivot chord”, this is a chord that can be found in both scales and allows you to “pivot” from one scale to the other. In this case writing Roman Numerals can show us how the music is moving from scale to scale (e.g. Chord I in C major, Chord IV in G major).
Unlike writing chord 1, chord 2, chord 3, etc. Roman Numerals can also tell us much more information about the chords.
2. Chord Qualities
If we write our understanding of chords as chord 1, 2, 3 etc. then we don’t have a simple way of seeing the quality of the chord (e.g. is it major, is it minor…?). In Roman Numerals we typically show this by using upper and lower case.
In a regular major scale, chords 1, 4 and 5 are major triads, chords 2, 3, 6 are minor triads and chord 7 is a diminished triad. So this would typically be written like this; chords I, ii, iii, IV, V, vi, vii.
A diminished triad also contains the same middle note (minor 3rd) as a minor triad and therefore it is also written as a lower case Roman Numeral.
So here is how we would show the chords in the scale of C major:
C major scale: C D E F G A B
Chord I - C E G
Chord ii - D F A
Chord iii - E G B
Chord IV - F A C
Chord V - G B D
Chord vi - A C E
Chord vii - B D F
Here we can see that we have C major, D minor, E minor, F major, G major, A minor and B diminished.
3. Inversions
As well as the quality of the triads, we can also show the inversion of the triads. An inversion in music refers to the order of the notes within the chord. A triad contains three notes, in the case of a C major triad these are C, E and G.
If we have a C at the bottom of this chord then this is called “Root Position”.
If we have the E at the bottom of this chord then this is called “First Inversion”.
If the G is at the bottom of this chord then this is called “Second Inversion”.
Many learning pianos believe that inversions refer to a specific order of notes on the piano. However, this is not the case. The inversion simply tells us which of the notes is the lowest. This means that if we have a C major triad spread over 6 notes like this: E G E C G C. This is a C major triad because it contains the notes C, E and G and it is also first inversion because the lowest note is the middle note of the triad, which is an E.
When using Roman Numerals, we can add this information by adding an “a”, “b” or “c” next to the Roman Numeral. Using the key of C major and therefore the scale of C major, if we saw “Chord Ia”, then this would refer to a C major triad in root position, “Chord Ib” would refer to a C major triad in 1st Inversion and “Chord Ic” would refer to a C major triad in 2nd Inversion.
Matthew Cawood
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