Struggling with chord progression notation? Whether you're analyzing, composing, or exploring modal harmony, this guide breaks down the two main Roman numeral systems—so you can write progressions with confidence and clarity!

For readers struggling with how to properly represent chords in different keys and modes, this guide provides a clear, structured explanation, including examples and practical applications. It also addresses the challenge of notating borrowed chords and modal progressions, making it easier for musicians to work with more complex harmonic structures.

There are indeed two primary ways to write chord progressions using Roman numerals, and understanding the difference is crucial for analyzing and composing music. The two methods relate to how you represent the quality (major, minor, diminished, augmented) of the chords within a key.

Here's a breakdown of the two methods:

Method 1: Using Case (Uppercase and Lowercase) to Indicate Chord Quality

This is the most common and generally preferred method for representing chord progressions. It relies heavily on the established conventions of using uppercase Roman numerals for major chords, lowercase Roman numerals for minor chords, and specific symbols for diminished and augmented chords.

This is the traditional notation commonly found in classical music.

• Uppercase Roman Numerals (I, IV, V): Represent major chords.
• Lowercase Roman Numerals (ii, iii, vi): Represent minor chords.
• Lowercase Roman Numerals with a "°" symbol (vii°): Represent diminished chords.
• Uppercase Roman Numerals with a "+" symbol (V+): Represent augmented chords (though augmented chords are rarer in basic diatonic progressions). The "aug" suffix can also be used.

How it Works:

1. Determine the Key: First, you need to identify the key of the music you are analyzing or writing. This will determine your "I" chord (the tonic).
2. Identify the Chords: Analyze each chord in the progression to determine its root and quality (major, minor, diminished, augmented).
3. Assign Roman Numerals: Assign a Roman numeral to each chord based on its relationship to the key's tonic and its quality:
   • In a major key, the diatonic chords (chords naturally occurring in the key) are: I, ii, iii, IV, V, vi, vii°.
   • In a minor key, the diatonic chords are: i, ii°, III, iv, v, VI, VII (Note: The v chord is often major, V, due to the use of the raised leading tone).
4. Write the Progression: Write the Roman numerals in the order the chords appear in the music.

Example in C Major:

I	ii	iii	IV	V	vi	vii°
C Major	D minor	E minor	F Major	G Major	A minor	B diminished

A typical progression in C Major might be: I - IV - V - I

Example in A Minor:

i	ii°	III	iv	v	VI	VII
A minor	B diminished	C Major	D minor	E minor	F Major	G Major

A typical progression in A Minor might be: i - VI - III - VII

Advantages of this method:

• Clarity: It immediately conveys the chord quality without requiring additional symbols for major and minor.
• Standard Practice: This is the most widely taught and used method, making it easier to communicate with other musicians.
• Readability: It's generally easier to read and understand, especially for longer progressions.

This notation is used in the free SHLD chord pack for chords in major and minor scales. You'll find dozens of great chords progressions, ready-to-use, as standard MIDI files!

Method 2: Using Roman Numerals relative to the Major scale

With this method, the Major scale serves as the reference scale, and all other scales or modes are notated in relation to this reference.

Additionally, the '♭' symbol can be added before the Roman numeral to:

• Show that the numeral itself refers to the diatonic position of the chord, but the flat symbol lowers the root by a half step.

A progression in the A minor scale would then be notated as:

i	ii°	♭III	iv	v	♭VI	♭VII
A minor	B diminished	C Major	D minor	E minor	F Major	G Major

Here, we can clearly see that the third degree is played a half step lower compared to the Major scale, or the Ionian mode (In A major the 3rd degree is C#, so C#b is C in A minor).

This notation allows for the creation of chord progressions in all kinds of modes or exotic scales, and even for mixing multiple scales—something that traditional notation does not allow.

For example, all the chords in different modes can be notated as follows:

Mode	Tonic	Supertonic	Mediant	Subdominant	Dominant	Submediant	Subtonic /Leading tone
Ionian (major)	I	ii	iii	IV	V	vi	vii°
Dorian	i	ii	♭III	IV	v	vi°	♭VII
Phrygian	i	♭II	♭III	iv	v°	♭VI	♭vii
Lydian	I	II	iii	♯iv°	V	vi	vii
Mixolydian	I	ii	iii°	IV	v	vi	♭VII
Aeolian (natural minor)	i	ii°	♭III	iv	v	♭VI	♭VII
Locrian	i°	♭II	♭iii	iv	♭V	♭VI	♭vii

If you see ♭II in a chord progression, there's a good chance that some chords have been borrowed from the Phrygian or Locrian modes—the famous Borrowed Chords 😊. Phrygian is the main source of ♭II in common harmony, while Locrian is rarely used for borrowing.

Variations of this notation can sometimes be found, such as ii being written as iim or IIm. In all three cases, it represents a minor chord. You might also see ♭IIIM, which is identical to ♭III but emphasizes that it's a major chord on the third degree rather than a minor one, as it would be in the major scale.

This notation is used in the SHLD free chord pack for modal chords.

If anything is still unclear or you have more questions about chord progression notation, feel free to contact me below or on my Patreon!