How to work with chord ear training
The module plays a chord and asks for its type. The first level offers only major and minor, the distinction everything else hangs on. Diminished and augmented follow, then the four-note chords: dominant seventh, major seventh, minor seventh and half-diminished seventh.
Chords are played either broken or as blocks. Broken, one note after another, is easier at the start because you can follow each note individually. Block chords are harder and at the same time more realistic, because that is how chords appear in music. Begin broken and switch once you reliably score above eighty per cent.
Make a point of singing the root. If you hold the root and hear the chord above it, the character of the chord stands out far more clearly. It is the one trick that really carries you through the four-note chords.
What chords are built from
A triad is formed by stacking two thirds on a root. Major third plus minor third gives major, minor plus major gives minor, two minor thirds give the diminished triad and two major thirds the augmented one. Counted in semitones: major 0–4–7, minor 0–3–7, diminished 0–3–6, augmented 0–4–8. The entire chord vocabulary of major–minor tonality hangs on that small table.
Four-note chords add one more third. The dominant seventh (0–4–7–10) is a major triad with a minor seventh and sounds charged, because the tritone between its third and seventh presses for resolution. The major seventh chord (0–4–7–11) adds a major seventh and sounds soft and suspended. The minor seventh (0–3–7–10) sounds settled, the half-diminished (0–3–6–10) pale and unresolved.
The impression does not come from the numbers but from the position of the third. The major third sits very close to the pure ratio 5:4 and reads as bright; the minor third, near 6:5, reads as darker. Everything else ever said about major and minor is cultural history. The acoustic core is that single note.
From practice
When major and minor will not separate, it helps to play the same chord twice in a row and change nothing but the third. That direct back-to-back comparison works almost immediately, while hearing isolated single chords stays uncertain for a long time. You can reproduce it here by repeating the same question and listening to the resolution before moving on.
For four-note chords, ask what the chord wants. Does it want to go somewhere? Then it is usually a dominant seventh. Does it stand still and sound soft? Then it is a major seventh. That functional question is more useful in daily practice than counting thirds.
Connect the training to an instrument early. Play the chord you just heard on guitar or piano. Linking sound, shape and name anchors the knowledge three times over, and it is why instrumentalists usually progress faster in ear training.
Common mistakes
Minor and diminished are often confused, because both have a minor third. The difference is the fifth: minor has a perfect one, diminished a flattened one. Listen specifically to the top note rather than the overall impression.
Inversions throw many people. A major triad in first inversion sounds different to an untrained ear than one in root position. On higher levels the module plays inversions too; that is deliberate, not a fault in the program. The way through is to ask for the lowest note and then for the stack of thirds, instead of judging the overall colour.
And the classic: moving to hard levels too soon. Anyone below ninety per cent on major and minor has no chance with four-note chords and only loses motivation. The levels are a ladder, not a menu.