I've been playing the bass for several years now and want to learn how to play jazz. I started out learning classical music because before the bass, I played the violin, so it just came easier for me. In my quest to learn as much as I can about playing jazz, I've come across sites like this that heavily encourage using a number system for learning music. So they say things like 2, 5, 1.

But, I just don't see the point of labeling sounds with numbers instead of using note letters. If you have relative pitch (which I have) you already know the relationship of the notes that you're hearing. Having to change my entire thought process for labeling just seems unnecessary. Am I missing something?

For anyone in here that plays jazz, do you use a numbering system? And in your honest opinion, do I really need to learn this system?

  • I don't get it. I looked at the site you linked to, but couldn't find an example of the numbering scheme you were talking about. Are these numbers the same as Roman numerals for chords? Are they scale degrees? Or what? Commented Jun 11, 2022 at 5:03
  • @aparente001 - scroll down a bit 18" should find that section.
    – Tim
    Commented Jun 11, 2022 at 11:47
  • You clearly are missing some stuff, if your relative pitch, that mean you don’t know the absolute note? It mean you can only tell the difference like a chord change which is precisely the thing which is numbered. You know it’s a 2-5-1, but you don’t know if it C or the absolute notes cause that is absolute pitch Commented Jun 11, 2022 at 18:33
  • also a chord progression is more to it. Or even a melody we all recognize melodys like happy birthday that is relative pitch. But a lot would not recognize that if it is precisely in c major or a different key until heard relative Commented Jun 11, 2022 at 18:35
  • That what numbers are. It’s like saying the name of a song, and we all know the song. It that simple. Commented Jun 11, 2022 at 18:36

7 Answers 7


As a bassist who has played predominantly jazz for decades I can say understanding and being comfortable with the number system is necessary if you want to progress to be an advanced player. Here are just a few reasons why:

  1. It allows you to associate chord progressions to any key and be able to transpose songs quickly and easily.

  2. It is a standard and accepted method of communication between jazz musicians, i.e.: “Does this blues have a 2-5-1 or a 5-4-1 turnaround?”

  3. It is part of the vocabulary for the understanding of jazz harmony and theory.

If I were to think about it more I’m sure I could come up with a few more reasons.

Now that’s not to say that it is all a numbers game. We must still be able to relate to notes and chords on a letter system as well and know our 12 keys and cycle of 5ths intimately. As a jazz musician if I’m playing say “Take the A Train” in C I am thinking of the letter chords:

  C / / / |  / / / / | D7 / / / |   / /  / / |
Dm7 / / / | G7 / / / |  C / / / | Dm7 / G7 / ||

At the same time I am thinking:

I - II7(or V/V) - IIm7 - V7 - I - IIm7 - V7

If I have to play it in Ab it’s easy:

Ab-Bb7-Bbm7-Eb7 etc.

EDIT: It has been rightfully pointed out to me by @Lazy that my answer focuses solely on the harmonic aspects of the numerical system. My reason for this is because harmony is so much more often discussed as numbers than melody by jazz musicians. However I do think the numerical system for melody is just as important to learn and understand. There however is a bit of a vagueness to using the numerical system for melody in jazz. The reason I say that is conceptually some musicians may choose to use the numerical system based on the key of the song, i.e. in the key of G, A,B,C is 2,3,4. In the same key over an Am chord some may choose to think of those 3 notes as 1,2,3 of Am. The reason for that is jazz musicians are primarily improvisers. There are many different improvisational concepts but among the most used is to think of notes as the chord and passing tones of the chord being played and not the scale degrees of the key. I am among those who conceptualize melody based on the individual chords. Take “All The Things You Are”. It starts on the VIm chord with a 1 in the melody. To me it is a 3 in the melody of the VIm chord. It helps tie in the melody to the improvisation much better to me. That’s not to say it’s right or better then the other system, just another way of looking at things. This is something to be aware of and keep in mind.

Bottom line, knowing the number system will benefit you for the reasons listed above AND it will make you a better musician in the long run.

  • Thanks so much John Belzaguy! That makes a lot of sense. This really helped me knowing that jazz musicians think both at the same time! Commented Jun 11, 2022 at 0:09
  • Just to clarify: Using numbers for chord analysis is not a Jazz thing, but common practice in music analysis for well over 200 years. What this is talking about is using numbers for actual notes. So in C major the melody c e f a would be 1 3 4 6 when harmonically we’d just consider this as I IV. So this is in fact some sort of streamlined relative base solfeggio.
    – Lazy
    Commented Jun 11, 2022 at 8:10
  • @Lazy Yes of course using numbers for harmony predates and is not exclusive to jazz. However, when jazz players refer to numbers they are talking about harmony, not melody. The OP did mention single notes but his example implies a ii V I progression. When referring to melody it’s common to say “5th” instead of “5”, i.e. it starts on the 5th and ascends diatonically to the 3rd. Commented Jun 11, 2022 at 10:50
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    @JazzNeophite My pleasure, good luck on your journey. If you don’t think of both then you’re limited to playing and understanding things in the key you learn the song in. If the first chord in “All The Things You Are” is just an Fm to you, you will be able to play the song in Ab, maybe even very well but you won’t understand the beauty of the harmonic progression it contains, VIm-IIm-V7-Imaj7-IVmaj7 modulation to the M3, etc. This song is hard enough to transpose even when you know it well but knowing the chord relationships in all the keys it works through is a HUGE help. Commented Jun 11, 2022 at 11:03
  • @JohnBelzaguy Don’t worry, When non-jazz players refer to number they usually mean harmony as well. But the page linked by the OP clearly uses the numbers for melody.
    – Lazy
    Commented Jun 11, 2022 at 18:17

Necessary, no, but the number system has become the de facto common language for jazz players. It's convenient, because it describes sounds regardless of the key. Naming the chords/notes themselves is comparatively cumbersome. There is only one "ii-V-I", but there are twelve "Dm7-G7-CM7", "Ebm7-Ab7-DbM7", etc.

If I say to another jazz player "go to the VI chord here" or "this is a ii-V", then it doesn't matter what key we're in, or even if we've transposed the piece, that player understands what sound I'm referring to.

Actually, a stronger statement: if you want to play jazz with anyone beyond a beginning experience level, then yes, you need to learn the numerical language.

  • 2
    Yes, and it is also more immediately informative about the structural function of the harmony, even if there's a small extra step to see what notes to play. Commented Jun 10, 2022 at 21:34
  • 1
    Thanks Aaron and Paul Garrett! I didn't expect to see such a fast response in here. That makes sense what you all are saying. I just have to put in the work now. Commented Jun 10, 2022 at 21:43
  • @Aaron As I stated in my comment to John: This here is not about roman numeral harmonic analysis (which is by no means a Jazz thing), but about specifying melodies as scale degrees. Of course the rationale stays the same, it makes transposing easier (but at the same time complex music much harder, which is no problem, because it is Jazz and Pop and no sort of complex music).
    – Lazy
    Commented Jun 11, 2022 at 8:13
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    @Lazy Neither John nor I are writing about harmonic analysis. However, Roman numerals are absolutely standard communication tools in jazz for specifying chord changes. The OP is generally asking about this article, which is about Roman numerals for this purpose.
    – Aaron
    Commented Jun 11, 2022 at 16:03

From a jazz perspective - although a lot of pop musos benefit from it - it just makes life a lot more simple. You probably are half way there already. Knowing I (1), IV (4) and V (5) of most keys.

Saying to the band 'This has a 1 6 4 5 intro' should mean everyone just jumps straight in, rather than having to say, in key C 'Intro's C Am F G', or key E♭ 'Intro's E♭ Cm A♭ B♭'. It should be almost a given!

Yes, it's pretty well an extension of NNs, which has been around for about 70-odd yrs now, a sort of extension of the RN analysis,but not for analysis purposes, purely for playing. And in jazz, using different keys is commonplace. No need to remind the players that 6 is minor - it's expected, etc. And simple!

  • Would you include a brief explanation of your abbreviations NN and RN? Commented Jun 14, 2022 at 2:38
  • @aparente001 - Nashville Number System, and Roman Numeral Analysis.
    – Tim
    Commented Jun 14, 2022 at 6:14

It's very useful to know, and if you have good relative pitch, it's a no-brainer - it's just understanding how to verbalize and write down the relationships between pitches that you already understand. It doesn't take much effort.


I play bass in worship team of our church for several years. I have to say it is necessary. I was learning modern piano when I was 8, it was a quick lesson that teach you only in number system, no classic piano stuff. Since then, I was trained to read notes by listening to the melody. I can write down the notes, like 1-1-5-5-6-6-5, for do-do-sol-sol-la-la-sol no mater what key it is. This might make me confused when reading notes in absolute pitch, but the relative notes that I memorized in number system make me easy to change key to suit vocal guy's demand. If you can sing out do-do-sol-sol-la-la-sol when listen to Twinkle, Twinkle Little Star, then the number system is easy to learn for you.

  • 1
    This seems to imply, that numbers are used instead of note names, whereas the other answers take for granted, that they represent chords. I share the latter assumption but I also admit, that the question should have stated this more clearly.
    – guidot
    Commented Jun 13, 2022 at 15:53
  • 1
    I took melody as example, but I also interpret the chord from music as number in my head. I play bass this way, instead of using A G D. Chords in number make the structure of progress clear and easy to change the key. The question did not state that clear, but as a bass player, we know that between the main chords, there is tons of melody to fill in.
    – Moses
    Commented Jun 14, 2022 at 2:27
  • OP's example of 2-5-1 can only be chords - but on bass, you'd root them initially, so same thing. Certainly not melody!
    – Tim
    Commented Jun 15, 2022 at 14:01

You use the numbering for two main reasons:

  • To show the relative relationship of chords, because those relationships function the same regardless of what key you are in. ii V I is basically doing the same thing harmonically whether it's Dm G C or Fm Bb Eb, etc. etc. Numerically we know that progression is roots moving by descending fifths.
  • The numbers tell us about chords relative to the tonic. If I write a progression C G, it isn't immediately clear what the functions of the chords are. It could be C: I V or G: IV I. Using the numbers clears up that ambiguity. A C chord isn't just a C chord. C: I is a tonic chord while G: IV is a subdominant chord. Within the context of a key a tonic chord and subdominant chord feel and sound totally different!

Jazz and classical musicians use this system.

If you don't want to learn it, you will be missing a major part of a musician's harmonic vocabulary. Conversations about harmony can be really tedious when someone doesn't know the common terms.

  • And numbers are shorter words, that roll off the tongue better, than "dominant," "subdominant," etc. Commented Jun 14, 2022 at 2:41

As @John-Belzaguy noted, the number system is efficient and enables musicians to communicate and change keys quickly.

Another reason to use it: it's commonly encountered in studio work and professional rehearsals, both of which may bypass traditional notation entirely.

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