Progression
Key
Roman numerals, decoded
Numerals name chords by scale position, independent of key: uppercase = major, lowercase = minor, ° = diminished. In any major key the pattern is fixed - I, ii, iii, IV, V, vi, vii° - which is why a progression learned once transfers to all 12 keys. Hear each chord alone in the chord player.
Play along
Set a comfortable tempo and strum or comp along - the highlighted chord card shows where you are. Pick out the chord tones on the online piano, and keep your timing honest afterwards with the metronome.
Chord Progression FAQ
What is a chord progression?
A sequence of chords played in order, usually repeating - the harmonic skeleton of a song. Progressions are written in Roman numerals (I, IV, V…) representing scale degrees, so the same progression can be played in any key: I-V-vi-IV in C major is C-G-Am-F, and in G major it is G-D-Em-C.
Why do so many songs use I-V-vi-IV?
It balances every pull a listener wants: home (I), tension (V), emotional shade (vi), and warm departure (IV), in a loop that resolves smoothly back into itself. It is so common that a famous comedy medley plays dozens of hits over this single repeating progression. Familiarity also compounds - audiences process it effortlessly, so writers keep reaching for it.
How do I use this for ear training?
Pick a key, play each progression a few times, and learn its character - the 50s progression sounds instantly nostalgic, ii-V-I sounds jazzy, vi-IV-I-V sounds anthemic. Then test yourself: have the player run a progression you chose without looking and name it by ear. Recognizing progressions is the fastest route to figuring out songs.
Can I change the key and tempo?
Yes - all 12 keys and 40-200 BPM. Each chord lasts one bar (four beats). Slower tempos help you hear each chord change; song-typical tempos (90-120 BPM) let you strum or play along.
What progression should I write my first song with?
I-V-vi-IV or I-IV-V-I. Both are forgiving, sound complete immediately, and thousands of great songs prove they are not a limitation. Write the melody over the loop first, then experiment with swapping one chord at a time - changing the vi to a ii is often the first interesting discovery.