Each trial plays four piano chords in a row. Your job is to recognize the pattern of the progression, not the exact key.
Progressions are written in Roman numerals: I is the home chord (tonic), IV and V are the chords built on the 4th and 5th steps of the scale, and lowercase numerals like vi are minor chords.
By default the key changes every trial, so you must listen to the relationships between the chords rather than memorizing absolute sounds.
Difficulty levels:
Easy: I–IV–V–I, I–V–vi–IV, I–vi–IV–V, I–IV–I–V
Medium: adds vi–IV–I–V and I–ii–V–I
Hard: adds I–iii–IV–V and I–V–IV–I
Tips:
Focus on where the music feels "at rest" (the I chord) and where it feels like it is pulling forward (the V chord).
Minor chords (ii, iii, vi) have a darker, softer color than major chords — learning to spot them quickly narrows down the options.