AI chord progression analysis: how to analyse, continue and reharmonize your chords

You have four chords that loop nicely, but the song does not go anywhere. Or you have a jazz standard in front of you and want to know why a Db7 appears before Cmaj7. An AI chord progression analyzer can answer both questions in a few seconds: it reads your chord symbols, names the key, writes the Roman numerals and proposes ways to continue or reharmonize.

It is a real help, but it is not magic. This guide explains what AI does well with harmony, where it goes wrong, and a concrete workflow with three worked examples (a pop loop, a jazz ii-V-I and a folk progression) so you can judge every suggestion on your guitar.

In short: an AI chord progression analyzer reads chord symbols (not audio) and returns the likely key, a Roman numeral analysis, possible continuations and reharmonizations. It is fast and usually right on diatonic progressions, less reliable on modal or ambiguous loops, and it never hears your melody. Use it for ideas and a second opinion, then play every suggestion and keep only what your ear accepts.

What AI is good at with chord progressions

An AI analyzer works on text: a list of chord symbols such as C G Am F. From that list it can do four useful jobs.

Naming the key

It compares the chords with the diatonic chords of every key and picks the best fit. For C G Am F it will say C major, with a nod to A minor, its relative. On progressions that stay inside one key, this is reliable and instant.

Roman numeral analysis

Once the key is set, it numbers each chord: I-V-vi-IV for C G Am F. This Roman numeral analysis is what lets you transpose, compare songs and spot non-diatonic chords. If the notation is new to you, read our guide to Roman numeral chord progressions first: you will judge the AI's answers much better.

Proposing continuations

Given where your chord progression stops, it suggests what could come next: a cadence to close a section, a move to the relative minor, a borrowed chord for a darker turn. Each suggestion comes with a short reason, which is where you learn.

Reharmonizing

Reharmonization means keeping the musical role of a passage while changing its chords. The classic moves an AI will propose:

• Tritone substitution: replace a dominant seventh with the one a tritone away (Db7 instead of G7 before C).
• Secondary dominants: put the V7 of a chord in front of it (E7 before Am, A7 before Dm).
• Borrowed chords from the parallel minor, also called modal interchange: Fm instead of F in C major, Bb (♭VII) instead of G.
• Extended chords and slash chords: Dm9, G13, Cmaj9, or C/G for a pedal bass.

Its limits: what AI does not know about your song

• It does not hear your song. It reads chord symbols, not audio. It does not know your melody, your rhythm or how long each chord lasts unless you tell it.
• It can be confidently wrong. Modal loops (D C G D), songs that hover between a major key and its relative minor, and short progressions with few chords can be read in two ways. The AI picks one and states it calmly.
• Style matters. A tritone substitution is idiomatic in a jazz ballad and odd in a campfire song. If you do not give a style, suggestions often drift towards jazz colours.
• The melody decides. A reharmonization that sounds great alone can clash with the note your singer holds. Only your ear and your guitar can check that.

Rule of thumb: treat every AI answer as a hypothesis, then test it by playing.

A workflow with the GuitarHarmony AI analysis

The GuitarHarmony AI analysis is built for this job. You type a progression of 2 to 32 chords; you can add three optional fields (key, style, intent such as "modulate to G" or "jazzier"). It returns:

Output	What it contains	How to check it
Detected key	One key, sometimes a mode ("D Mixolydian")	Which chord feels like home when you loop it?
Analysis	2 to 4 sentences with Roman numerals	Number the chords yourself, compare
3 continuations	3 to 6 chords to add, each with a one-line reason	Play your loop, then the addition
2 to 3 reharmonizations	The same progression with new chords, each explained	Play it under the melody, not alone

A practical routine:

1. Type the chords exactly as you play them (C G Am F, not "the Let It Be chords").
2. Set the style. Add an intent if you have one ("keep it simple", "darker chorus").
3. Read the key and the analysis first. If the key is wrong, nothing else will be right: add the correct key in the options and analyse again.
4. Click "Add to my progression" on a continuation, or "Replace my progression" on a reharmonization, then play the result on your guitar.
5. Keep one idea, reject the rest, and write down why.

On a free account, each analysis uses 1 credit and every new account starts with 5 free credits; with Premium, analyses are unlimited and no credits are needed.

The three examples below show the kind of output you get. The wording and the exact chords vary from one request to the next, which is precisely why the judging step matters.

Example 1: a pop loop (C G Am F)

Style: Pop. Typical result: C major, I-V-vi-IV, the I-V-vi-IV progression that runs half the charts.

• Continuations: Dm7 G7 C (a ii-V-I to close the section); E7 Am (the V of vi, pushing into the relative minor for a bridge); Fm C (iv-I, a borrowed minor plagal ending).
• Reharmonizations: C G/B Am7 Fmaj7 (a descending bass C, B, A with richer colours); C E7 Am F (E7 replaces G as a secondary dominant into Am); C G Am Fm (borrowed iv in bar 4).

How to judge: play each one under the melody. E7 contains G#: if the melody sits on G in bar 2, it clashes, so keep G there. Fm contains Ab: if the melody holds A over bar 4, Fm sounds wrong, but if it holds C or F, Fm is a lovely surprise. The G/B version is the safest and works with almost any pop melody, because only the bass and the colour notes change.

Example 2: a jazz ii-V-I (Dm7 G7 Cmaj7)

Style: Jazz. Typical result: C major, ii7-V7-Imaj7, the ii-V-I cadence.

• Continuations: Cmaj7 A7 Dm7 G7 (a I-VI7-ii-V turnaround back to the top); Cm7 F7 Bbmaj7 (the same cadence a whole step down, a common way to modulate); Bm7♭5 E7 Am (a minor ii-V into the relative minor).
• Reharmonizations: Dm7 Db7 Cmaj7 (tritone substitution); Dm9 G13 Cmaj9 (extensions); Dm7 G7♭9 Cmaj7 (a darker dominant).

How to judge the tritone substitution: it works because G7 and Db7 share the same guide tones, B and F. On the guitar, play the G7 shell 3-x-3-4-x-x, then Db7 as x-4-3-4-x-x: the F (4th string, 3rd fret) and the B (3rd string, 4th fret) do not move, only the bass slides from G to Db and then down to C. That smooth voice leading is why it sounds right. Now check the melody: a G over the Db7 becomes a #11 (fine), but a D becomes a ♭9 (harsh in a slow ballad).

Example 3: a folk progression (D C G D)

Style: Folk. This one is a trap. The chords D, C and G all belong to G major, so an analyzer may answer "G major, V-IV-I-V". A better answer is D Mixolydian, I-♭VII-IV-I: D is the chord the loop rests on, and the C natural is the flattened 7th that gives the open, Celtic sound.

If the detected key does not match the home chord you hear, enter "D Mixolydian" in the key field and analyse again. Then judge the suggestions with the style in mind:

• Keep: D C/D G/D D (all chords over a D bass, the open 4th string ringing as a drone); Dsus4 Cadd9 G D (open-string colours that sound natural on an acoustic).
• Use with care: A7 D as a continuation. It works, but A7 contains C#, which cancels the Mixolydian colour. That can be a deliberate brightening for a final chorus.
• Reject for folk: Dmaj9 C13 Gmaj7. Dmaj9 contains C#, which contradicts the C chord, and the jazz colours fight the strummed style.

AI analysis vs analysis by hand

Task	By hand	With AI
Key of a diatonic song	1 to 2 minutes with a table	Seconds, very reliable
Modal or ambiguous loop	Your ear decides the home chord	Often hesitates: give the key
Roman numerals	Slow at first, builds real skill	Instant, check against yours
Ideas to continue	Limited to what you already know	3 options with a reason each
Reharmonization	Needs vocabulary and time	Fast, explained, must be tested with the melody
Learning	Sticks because you did it	Sticks only if you verify and play

The best use is both: analyse by hand first (two minutes), then compare with the AI. When you disagree, you have found exactly the point worth learning.

Prompt tips if you use a general chatbot

General chatbots can do the same job if you give them the context a dedicated tool asks for:

• Give the chords bar by bar, with durations: "| C | G | Am | F F | (4/4, 2 bars of F)".
• Give the melody note on each chord if you know it. It is the single biggest improvement in reharmonization quality.
• Name the style and the instrument: "folk, strummed acoustic guitar, open chords only".
• Ask for the key and Roman numerals first, then the suggestions, and ask it to flag every non-diatonic chord and explain its function.
• Ask for 3 options ranked from safe to adventurous.
• Ask for chord names, not tablature. Chatbots often get fret numbers wrong; find the shapes yourself or in a dedicated tool.
• Never trust song attributions. If it claims "this is the progression of song X", check it.