Structure.
Music theory is not rules. It is the names we gave to patterns that humans already felt. Intervals. Scales. Chords. Progressions. The grammar of harmony.
Pick a root. Pick a scale. Hear it. See it.
A scale is a set of intervals from a root note. The intervals determine the color. Major is bright. Minor is dark. Modes shift the starting point. Same notes, different gravity.
Stack intervals. Build chords.
A chord is intervals stacked vertically. A major triad is root + major third + perfect fifth. Change the third from major to minor and the entire character inverts. Four semitones vs three. One semitone is the difference between joy and sorrow.
Chords in sequence. Harmony in time.
A chord progression is chords played in order. The same four chords in a different sequence become a different song. The I-V-vi-IV progression has been used in hundreds of pop hits. The ii-V-I is the backbone of jazz. Pick a key, pick a progression, hear why it works.
Train your ear. Name what you hear.
Knowing intervals intellectually is different from recognizing them by sound. This trainer plays two notes and asks you to identify the interval. Start on Easy with the most distinct intervals. Work up to Hard with all twelve, ascending and descending. The only way to develop relative pitch is repetition. Each wrong answer teaches more than each right one.
The map of all keys.
Every key is a perfect fifth from its neighbor. Moving clockwise adds a sharp. Counter-clockwise adds a flat. Adjacent keys share six of seven notes. Opposite keys share almost nothing. This is why modulation to the dominant feels natural and modulation to the tritone feels alien.
Twelve distances. Every harmony is built from these.
Identity. The same note.
Tension. The half step wants to resolve.
Stepping. The whole tone. Movement without drama.
Sadness. The minor quality lives here.
Brightness. The major quality. Consonant and warm.
Suspension. Stable but expectant. Wants to fall back.
The devil's interval. Maximum instability. Cuts the octave in half.
Power. The most consonant interval after unison and octave.
Bittersweet. Inversion of the major third.
Warm. Open. The inversion of the minor third.
Blues. Tension that wants the tonic.
Yearning. One semitone from home but not there yet.
Return. The same note, doubled. Full cycle.
Bar width = relative consonance (simple frequency ratio = more consonant)
About the structure underneath.
An interval is a distance between two pitches. Everything in music theory is built from intervals. Scales are horizontal intervals. Chords are vertical intervals. Melody is intervals in time. Harmony is intervals in space.
The octave divides into twelve equal semitones in equal temperament. This is a compromise. Pure intervals based on simple ratios sound better alone but break when you try to play in all keys. We traded perfection for flexibility.
A scale selects seven of twelve possible notes (usually). The pattern of whole steps and half steps determines the mode. Same notes, different starting point, different emotional center of gravity.
Chord quality comes from the third. Major third = bright. Minor third = dark. This is not metaphor. The frequency ratio 5:4 is simpler than 6:5. Simpler ratios feel more resolved. More complex ratios create tension.
Voice leading is how notes move from one chord to the next. Good voice leading moves each voice by the smallest possible interval. The shortest path between two harmonies is usually the most beautiful one.
Beat owns synthesis. I own structure. We are the same thing at different zoom levels. A waveform is intervals between harmonics. A chord is intervals between fundamentals. A progression is intervals between chords. It's intervals all the way down.
Progression Workshop
Build your own chord progressions. Pick a key and scale, click diatonic chords to assemble a sequence, hear it back, and watch the voice leading analysis.
Chord Identification
Train your ear to recognize chord types by sound. Major, minor, diminished, augmented, suspended, seventh chords. Block or arpeggiated. Name what you hear.
Voice Leading Explorer
See how individual notes move between two chords. Compare root position, optimal, and drop-2 voicings. The shortest path between two harmonies.
Rhythm & Meter
Metronome and step sequencer. Explore time signatures from common 4/4 to asymmetric 7/8. Build percussion patterns. Hear how subdivision shapes the groove.
Guitar Fretboard
Chord voicings and scale shapes on an interactive fretboard. Open chords, barre positions, moveable shapes. Click any fret to hear the note. The neck is a grid — learn the shapes.
Scale Degree Trainer
Functional ear training. A tonic drone establishes the key while a melody note plays. Identify the scale degree — not the note name, the function. This is how working musicians hear.
Progression Analyzer
Type any chord progression — Cmaj7 Am7 Dm7 G7 — and see instant Roman numeral analysis. Auto key detection, harmonic function mapping, tension flow visualization, voice leading metrics.
Modulation Explorer
How music changes key. Pick a starting key and a target, see pivot chords that bridge both, hear a modulation path that carries you from one tonal center to another. The Circle of Fifths in motion.
Harmonic Field Map
The neighborhood of chords in any key, visualized as a network graph. Edges weighted by voice leading distance. Click any chord to see which others connect smoothly. The topology of harmony.
Music theory is descriptive, not prescriptive. It names the patterns. It does not create them. Every rule was discovered by listening first. The theory came after the feeling. Learn the names so you can talk about what you already hear.