The next unit is about how chords function together in a key. That material assumes you can look at a chord and identify it without hesitation. If you're still working through the mechanics of building triads or figuring out seventh chord types, spend more time here before moving on. Seriously.

You learned that a triad is three notes built by stacking thirds: root, third, fifth. The quality of those thirds determines the triad's quality.

Major triads stack a major third then a minor third. Minor triads flip it: minor then major. Both have a perfect fifth from root to top. Diminished triads stack two minor thirds (diminished fifth). Augmented triads stack two major thirds (augmented fifth).

You learned that the diatonic triads in any major key always follow the same pattern: major, minor, minor, major, major, minor, diminished.

Practice: Note Trainer (chord mode)

You learned to think of the musical alphabet in thirds, skipping every other letter. That trick lets you spell any triad instantly: pick a root, skip a letter, skip a letter. Then adjust the quality with sharps or flats.

You also learned that a third always spans three letter names, no matter how many half steps are involved. That's the difference between the interval's number (letter-name distance) and its quality (half-step distance).

You learned that rearranging which note is on the bottom of a chord is called inversion. A triad in root position has the root on the bottom. First inversion puts the third on the bottom. Second inversion puts the fifth on the bottom. The chord is still the same chord regardless of inversion.

You learned that stacking one more third onto a triad gives you a seventh chord. The three most common types:

• Major seventh (maj7): major triad + major 7th
• Minor seventh (m7): minor triad + minor 7th
• Dominant seventh (7): major triad + minor 7th

The dominant seventh is the odd one out: the triad and seventh quality don't match, and that mismatch creates tension.

Practice: Note Trainer (chord mode) | Interval Trainer

You learned that sus chords alter the third: raise it one scale step for sus4, lower it one scale step for sus2. Without a third, the chord is neither major nor minor.

Add chords keep the third and tack on an extra note. An add9 is a triad plus the 9th (which is not the same as sus2, because the third is still there).

This pulls from the entire building chords unit.