Volume 1 gave you the four-chord loop, the relative minor, the tritone pull, voice leading and the circle of fifths. This volume goes one layer deeper, into why individual notes and chords carry the feelings they do. Every accelerator has a button; press it, then read why it works. (Everything here uses the piano's equal-tempered tuning, with A above middle C at 440 Hz, and all sound is generated in your browser.)
Build a chord by stacking notes from a root. Go up 4 half-steps (a major third) and you get a major chord: open, bright. Go up only 3 (a minor third) and the same chord turns minor: shadowed, inward. The top note, a fifth above the root, stays put. Western listeners tend to hear major as happy and minor as sad, though that link is learned and culture-dependent, and plenty of joyful music is in minor.
C major = C + E + G. C minor = C + E♭ + G. Only the middle note moves, down one half-step.
The C major scale is C D E F G A B. The tight half-step pairs are E–F and B–C, and those are where clashes come from. Remove F and B and you get the major pentatonic: C D E G A, five notes all a whole step or more apart. That's why you can noodle randomly on it over a drone and it still sounds like music. The piano's black keys happen to form a pentatonic scale too, which is why kids can improvise on them. Folk songs, blues licks and rock guitar solos lean on pentatonic scales all over the world.
Press each a few times. The phrases are random every time.
Number the chords by the scale step they're built on: I (home), IV (four steps up) and V (five). The classic twelve-bar blues runs I I I I | IV IV I I | V IV I I, then repeats. Lyrics often follow it too: a line, the same line again over the IV chord, then an answering line over V. Blues players usually make every chord a "seventh" chord, adding a note that gives the whole form its gritty, unresolved color.
In C: C7 C7 C7 C7 | F7 F7 C7 C7 | G7 F7 C7 C7.
Musicians often line the modes up from brightest to darkest: Lydian, Ionian (the major scale), Mixolydian, Dorian, Aeolian (natural minor), Phrygian, Locrian. Walk down the ladder and exactly one note drops a half-step at every rung. Dorian, a minor mode with a raised sixth, is the sound of "Scarborough Fair," Miles Davis's "So What" and "Oye Como Va"; Lydian, with its raised fourth, floats through the Beatles' "Blue Jay Way."
Pick a rung, starting at 1.
On C: Lydian C D E F♯ G A B; Ionian lowers F♯ to F; Mixolydian lowers B to B♭; Dorian lowers E to E♭; Aeolian lowers A to A♭; Phrygian lowers D to D♭; Locrian lowers G to G♭.
In C major the IV chord is F (F A C). Borrow its minor version from C minor, Fm (F A♭ C), and one note slides down a half-step on its way home. Songwriters reach for this when they want nostalgia or heartbreak in a major key. Radiohead's "Creep" (1992) is built on G – B – C – Cm: the last chord is exactly this move, IV going to minor iv. (Its progression and melody resemble the Hollies' "The Air That I Breathe," whose writers were later added to the credits.)
1. G major is G, B, D. What is G minor?
- G, B, D♭
- G, B♭, D
- G♭, B, D
Answer: G, B♭, D. Only the middle note moves, from 4 half-steps above G to 3.
2. Which two notes do you remove from C major to get C major pentatonic?
- D and A
- F and B
- E and G
Answer: F and B, the notes that sit a half-step from a neighbor (E–F, B–C). Without them, nothing rubs.
3. In the twelve-bar blues, which chord is in bar 9?
- I
- IV
- V
Answer: V. The last line goes V – IV – I – I, the turnaround that pulls you back to the top.
Small moves carry big feelings. One half-step turns major into minor and lowers a mode one rung darker; removing two notes gives the clash-free pentatonic; three chords in twelve bars built the blues; and a single borrowed chord makes a major key ache. Theory is a map of those small moves.
Try this: on any keyboard or keyboard app, play only the black keys over a low held note and improvise for two minutes. Then find the minor iv in a song you love: listen for the moment a major-key chorus suddenly goes wistful.
Go deeper:
🌐 Hooktheory Trends (search real songs by chord progression)
📘 How Music Works by John Powell (a friendly explanation of scales, harmony and why they sound the way they do)
🌐 Related pieces in this library: Music Theory Accelerators (Vol. 1) · Rhythm You Can Feel