Progression
I – V – vi – IV
Key
C major
Tension
Moderate
Chord Progression in C major
I – V – vi – IV
C – G – Am – F
Chords
4
Tension
Moderate
Nashville
1 – 5 – 6 – 4
Inputs
Result
C major scale: C-D-E-F-G-A-B. I=C (major), V=G (major, tension 3), vi=Am (minor, tension 2), IV=F (major, tension 2). Average tension = (1+3+2+2)/4 = 2.0.
Inputs
Result
G major scale: G-A-B-C-D-E-F#. ii=Am (minor, tension 2), V=D (major, tension 3), I=G (major, tension 1). Average tension = (2+3+1)/3 = 2.0.
Inputs
Result
A natural minor: A-B-C-D-E-F-G. i=Am (minor, tension 1), VII=G (major, tension 2), VI=F (major, tension 2), v=Em (minor, tension 2). Average = (1+2+2+2)/4 = 1.8.
A chord progression is a sequence of chords built from scale degrees. In C major, a I-IV-V-I progression uses C, F, G, C. Each degree has a Roman numeral: uppercase for major chords, lowercase for minor. The most common pop progression is I-V-vi-IV.
| Degree | Quality (Major) | Quality (Minor) | Function |
|---|---|---|---|
| I / i | Major | Minor | Tonic (home) |
| ii / ii° | Minor | Diminished | Supertonic |
| iii / III | Minor | Major | Mediant |
| IV / iv | Major | Minor | Subdominant |
| V / v | Major | Minor | Dominant |
| vi / VI | Minor | Major | Submediant |
| vii° / VII | Diminished | Major | Leading tone |
The Nashville Number System replaces Roman numerals with Arabic numbers (1-7) to chart chord progressions. A "1-4-5" in any key means tonic, subdominant, dominant. Session musicians use it to transpose songs instantly without rewriting charts.
| Nashville # | Roman Numeral | In Key of C | In Key of G |
|---|---|---|---|
| 1 | I | C | G |
| 2 | ii | Dm | Am |
| 4 | IV | F | C |
| 5 | V | G | D |
| 6 | vi | Am | Em |
The I-V-vi-IV progression dominates pop music — used by "Let It Be," "No Woman No Cry," and thousands more. The I-vi-IV-V (50s progression) defined early rock. Jazz relies on ii-V-I. Blues uses I-I-I-I-IV-IV-I-I-V-IV-I-V (12-bar blues).
| Progression | Genre | Mood | Example Song |
|---|---|---|---|
| I-V-vi-IV | Pop | Uplifting | Let It Be |
| I-vi-IV-V | Rock/Pop | Nostalgic | Stand By Me |
| ii-V-I | Jazz | Sophisticated | Autumn Leaves |
| I-IV-V | Blues/Rock | Driving | La Bamba |
| i-VII-VI-V | Latin/Metal | Dramatic | Hit the Road Jack |
Chord tension describes how strongly a chord wants to resolve. The tonic (I) is stable with tension level 1. The dominant (V) has maximum tension (level 3) and strongly pulls to I. Subdominant (IV) and mediant chords sit at medium tension (level 2).
Use Roman numerals or Nashville numbers — they are key-independent. A I-IV-V in C (C-F-G) becomes D-G-A in D. Count the interval between old and new root, then shift every chord by that interval. The calculator handles this by changing the root note.
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Last Updated: Mar 25, 2026
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