In this lesson, we take triads and go a step further by stacking an additional third on top.
The first six exercises ask you to distinguish between major seventh chords and dominant seventh chords. Major seventh chords contain a major seventh interval, which is one of the more dissonant intervals, so make sure to listen for this. Dominant seventh chords are major triads with a minor seventh on top. These chords are called dominant chords because they generally lead to a resolving tonic chord in a chord progression. Play a G7 chord (G, B, D, F) and then follow it with a C major triad. Now try playing G7 followed by an A minor triad. Now play G7 followed by an Ab major triad. In all of these examples, note how the G7 chord always leads your ear towards another chord, which provides the final resolution you expect to happen. Dominant seventh chords lead your ear towards another chord much more than a major seventh chord (a major seventh chord could be the resolution of a dominant seventh chord - play G7 to Cmaj7).
Exercises 7-12 focus on fully diminished seventh chords and half-diminished seventh chords. Like dominant sevenths, fully-diminished sevenths serve a dominant function in chord progressions, meaning they always lead your ear to another resolving chord (usually a tonic chord). Half-diminished sevenths also lead to other chords (usually dominant chords), but have less pull on your ear than a fully-diminished seventh. The minor seventh interval between the root and seventh of the chord is also distinct because it is less dissonant in the context of the chord than the diminished seventh in the fully-diminished seventh chord.
Exercises 13-18 incorporate the minor seventh chord into the mix. Minor seventh chords have a distinctly different sound from diminished chords. The leading quality (needing a resolution) in diminished chords is not as present in minor sevenths. Overall, minor seventh chords have the least amount of dissonance out of the five most common types of seventh chords. Try playing a few minor seventh chords to hear how they sound different from either type of diminished seventh.