The Chord Family of a Key
Every key houses a family of seven chords: meet them by roman numeral from I to vii°, hear which are major and which are minor, and watch the pattern survive any key change.
Chords never live alone — every key comes with a whole family built in. Press play first and hear the preset I–IV–V–I go around. Then click the chord chips in the palette: each click writes that chord into the currently selected slot, sounds it as it lands, and moves on to the next slot. Swap all seven in, one by one, and meet the family.
Seven notes, seven chords
Take each of the seven notes of the major scale as a root and build skip-one-take-one twice on top of it, using only notes from the key. You get seven chords — the chips you just clicked. This family is called the diatonic chords, and the vast majority of pop chord choices come straight from it.
Roman numerals: universal house numbers
We number the family with roman numerals: I, ii, iii, IV, V, vi, vii°. Uppercase means a major triad (I, IV, V), lowercase means a minor triad (ii, iii, vi), and the little circle on vii° marks a diminished triad — darker and tenser than minor. The numeral names the scale degree, not any particular key.
Change the key, keep the pattern
Use the key picker to switch to G major or D major and click the seven chips into the slots again. Every actual note changes, yet the pattern of which degrees are major and which are minor does not budge: always I, IV, V major; ii, iii, vi minor; vii° diminished. That is the power of roman numerals — learn one pattern and it travels to every key.
Quiz
In a major key, which degrees are major triads?