Roman Numeral Notation in Music Theory

Instructor: Christopher Muscato

Chris has a master's degree in history and teaches at the University of Northern Colorado.

Ever seen Roman numerals in sheet music? Why are those there? In this lesson, we'll examine this notation system and see how it helps us understand the chord structure of a composition.

Roman Numerals in Music

Latin is a dead language. Still, there's a chance that you'll have to learn a bit of it if you're going to pursue a future in music. Sure, there's always the chance that you'll be singing some old church chant in Latin, but today we're not dealing with Latin words. We're dealing with Latin numbers.

It's not uncommon in sheet music to see Roman numerals, the ancient Roman counting system that used letters to denote quantities. I is one, V is five, X is get the idea.

Roman numerals are pretty common even today, but what are they doing in music? Basically, this is a way for composers to note the chords that are being used at any point in the music. It's a pretty common feature in Western music, so even though we may not be in Rome, it can still be good to do as the Romans do.

Roman numerals may often appear below the staff in sheet music
roman numerals

Roman Numerals as Chords

So, how does this work? Roman numeral notation represents chords as numbers (in Roman numerals), as opposed to letters. The number depends on the key of the composition.

The foundation of the Roman numeral notation system is the key of the piece. For example, you might say that a composition is in C major, or D sharp, or A minor. This reveals the tonal center of the composition, which determines the chord structure.

In any key, the chord with the same name is the tonic, or the root, and then you build up from there. For example, in the key of C major, the tonic chord would be C major. That's the first chord of the scale.

From there, you move up a step, so the second chord would start on D, the third on E, the fourth on F, the fifth is G, the sixth is A, and the seventh is B. Since the octave is the same chord as the root, just higher, we don't need to give it a different numerical designation for our purposes today.

As you can see, within every key, each chord has a numerical position that indicates the distance of that chord from the tonic. Now all we have to do is translate that into Roman numerals. The first, second, third, fourth, fifth, sixth, seventh, and octave become I, II, III, IV, V, VI, and VII.

So if you see a Roman numeral in sheet music, it just means that this part of the music is based on the chord that holds that numerical position in the key. In the key of C Major, if you saw a V below the staff, you'd know that the notes belonged the chord of G.

If this piece is written in C major, can you tell what chord is the basis of each measure? (Hint, the root of each chord is in red)

Different Symbols in Roman Numerals

If the Roman numerals are there to help you understand which chord those notes belong to, then why are some Roman numerals in upper case, while others are in lower case? That's because not all chords are the same. Different kinds of chords have different notations. There are four major ones.

  • When the Roman numerals are in upper case (I, IV, V, etc.), then the chord is major.
  • If the Roman numerals are in lower case (i, iv, v, etc.), then the chord is minor.
  • If the Roman numerals are in upper case with a plus sign next to them, then the chord is augmented (which indicates that it's been raised by a semi-tone).
  • If the Roman numerals are in the lower case with a small circle next to them, then the chord is diminished (indicating a minor or perfect that has been lowered by a semi-tone).

Chord Progression

These notations matter because every scale has a natural progression of major and minor chords.

Major Chord

In a major chord, that progression is major, minor, minor, major, major, minor, diminished.

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