Nashville Number Trainer
Numbers are chords with the key removed. Learn to think in them, and every song you know works in every key you can play.
The idea
Number the notes of any major scale 1 through 7, and build a chord on each. Now a progression isn't "G, C, D", it's "1, 4, 5", and that sentence is true in every key at once. Studio players chart entire songs this way: when the singer wants it a step down, nobody rewrites anything. The numbers don't move.
How to read them
A bare number is a major chord, a lowercase m makes it minor, and the little circle on 7 marks the diminished chord. In every major key the pattern is identical: 1, 4 and 5 are major, 2, 3 and 6 are minor, 7 is diminished. Memorize that one sentence and you know the chords of all twelve keys.
How to practice
Build progressions in the builder and watch the same numbers wear different chords in two keys side by side. Then switch to the quiz and drill both directions: number to chord and chord to number. Start with the easy keys, and when your streak stops resetting, open the pool to all twelve.
top: the number · middle: in G · bottom: the same chart in E