Number System in Music (Simple Explanation for Beginners)

October 20, 2023
Numbers image by Kirk Lai

A few years ago, a student of mine asked what’s the most important music theory concept I should learn? My response to his question was: Learn the Number System in music.

The number system in music is a super-efficient way to describe the notes and chord changes that are being played.

Here’s some of the benefits of learning this system:

  • You’ll understand music theory faster
  • You’ll be able to comprehend what you’re hearing in a more streamlined way (music theory and ear training go hand-in-hand)
  • You’ll be able to transpose any phrase, lick, or chord progression in any key
  • You’ll be able explain music more simply

If you want to accelerate your musical growth, this is the concept you’ll want to learn.

Let’s dive in.

TL;DR

If you’re short on time, watch my video The Number System in Music (A simple explanation for absolute beginners). In the video, I’ll breakdown this powerful system that’s widely used by professional musicians.

YouTube video
The Number System in Music (A simple explanation for absolute beginners)

What is the Number System in Music?

The number system in music is an efficient way of labeling any sound with a number. Sounds can be individual notes or chords.

So, instead of using letters, like C, D, E, and F these letters are labeled using Roman numerals or numbers (I, ii, iii, IV or 1, 2, 3, 4).

Number System and Roman Numeral System
Example 1: Number System and Roman Numeral System

Think in Numbers Instead of Letters

You may have heard of the Nashville Number System, or the Roman numerals System, or Roman numeral Analysis. They’re all basically the same thing, in that music is translated into numbers.

The main point is that you’re thinking in numbers instead of letters.

The structure of these numbers are also moveable. And this is where a lot of beginners with this system get confused.

This is not a fixed system. It’s a moveable system. So, the numbers that are used depends on the key of a chord progression or the root note of a chord or scale.

Sometimes, musicians use the numeric system to explain a chord progression, and other times they’re explaining a musical phrase, lick, or scale.

I’ve seen this system used for chord symbols, to transpose chords, understand and play musical transcriptions, describe a note of the scale, and play chord charts in a different key.

Context matters.

Roman numerals versus Regular Numbers

Keep these points in mind when using the number system in music:

  • If you’re referencing chords in a chord progression, use Roman numerals if you want to include chord quality.
  • If you’re referencing the notes of a chord or scale, use regular numbers.
  • If you’re referencing chord tones, embellishments, chord extensions, the number is in relation to the tonic of the chord and a regular number is used. eg: ii7♭5 (Roman numerals for the chord and regular number for the chord tones).

Why is the Number System more efficient than regular note spellings?

There are a couple reasons that makes regular note spellings inefficient:

  • Note spellings by themselves do not provide information as to their relation to the tonic.
  • Enharmonic spellings can get really confusing, especially when there’s a double flat or double sharp involved.
Inefficiency with spelling notes with letters
Example 2: Inefficiency with spelling notes with letters

Using numbers as labels eliminates both of these issues.

  • The number itself already tells you the interval that you’re hearing.
  • And no matter what key you’re playing, you’ll never come across a weird enharmonic spelling.
The Number System – A more efficient approach
Example 3: The Number System – A more efficient approach

How To Apply The Number System In Music?

The Major scale is the basis for the fundamental structure of the numeric system used in music.

Let’s first take a look at the structure of this scale.

A Major scale is built from the following intervals: Whole-Step, Whole- Step, Half-Step, Whole-Step, Whole-Step, Whole-Step, Half-Step.

When you play these intervals in sequence, they sound out the familiar Major scale (Do, Re, Mi, Fa, Sol, La, Ti). You may have heard of the song “Do-Re-Mi,” from the movie The Sound of Music. That song uses the notes of a Major scale and calls the notes out by Solfege.

Now, let’s change these labels (Do, Re, Mi, Fa, Sol, La, Ti) using regular numbers.

To apply the number system, all we have to do is change the labels of these notes:

  • Do becomes 1
  • Re becomes 2
  • Mi becomes 3
  • Fa becomes 4
  • Sol becomes 5
  • La becomes 6
  • Ti becomes 7
Structure of the Numeric System
Example 4: Structure of the Numeric System

Musical Structure of the Number System

The numbers 1, 2, 3, 4, 5, 6, 7 have the same structure as a Major scale. All the numbers are in direct relation to the 1.

So in other words:

  • 1 is the root note
  • 2 is a major second interval
  • 3 is a major third interval
  • 4 is a perfect fourth interval
  • 5 is a perfect fifth interval
  • 6 is a major sixth interval
  • 7 is a major seventh interval

Remember, the numbers are relative to the root note of a scale.

So, if you were to spell out a Major scale, you’d simply say: 1, 2, 3, 4, 5, 6, 7.

And, if you were to spell a Dorian scale, you’d say: 1, 2, ♭3, 4, 5, 6, ♭7.

The structure of a scale is still based off the structure of a Major scale. Flats and sharps are used to indicate where the structure is different.

How To Apply The Roman numeral System In Music? (Chord Notation)

If you want to apply this concept to chords, I highly recommend that you use the Roman numerals System, especially if you are including the chord quality.

The Roman numeral System creates a chord scale from the Major scale, and labels each chord in that chord scale with a Roman numeral. This system has become widely used by jazz musicians and is a streamlined way to write out any chords to a song.

So, if you were to create a chord scale of 7 chords from a C Major Scale, you’d get these chords:

  • C Major 7
  • D minor 7
  • E minor 7
  • F Major 7
  • G 7
  • A minor 7
  • B minor 7♭5 (half-diminished)

The Roman numeral system changes the labels of these chords to:

  • I
  • ii7
  • iii7
  • IV
  • V7
  • vi7
  • vii7♭5
Roman Numeral System for chords
Example 5: Roman Numeral System for chords

Notice a few things:

  • For Major 7 chords, the number 7 is not represented. It’s already assumed to be a major 7.
  • Minor chords use lower case Roman numerals.
  • The 7 for a minor chord is assumed to be a minor 7 (flatted 7).
  • The “♭” means flat.

This approach for labeling chords makes it super-easy to transpose tunes to any of the 12 keys in music. 

Jazz musicians often use this concept for analyzing tunes. This technique is called Roman numeral analysis.

Since thinking in numbers is a moveable concept, Roman numeral analysis simplifies analyzing jazz chord progressions that often change keys.

Now, It’s Your Turn

If you spend some time knowing the number system in music you’ll soon realize how efficient it is.

This is a system and language that’s become a standard among studio musicians, jazz players, and many other styles of music.

When you understand how this all works, you’ll communicate your musical ideas more clearly to other musicians. And, you’ll do it with confidence.

Start slow. Focus few tunes. Then, analyze the melody as numbers, and also do a Roman numeral analysis on the chord changes.

You can get the hang of this in a matter of weeks if you make it a habit to think in numbers.

Click here for more bass guitar lessons and jazz theory like this.

PosidoVega

Hi! I’m Posido Vega, a multi-passionate creative. I’m an artist, bass player, jazz theory enthusiast, children’s book author and illustrator, and SEO 😅.

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