02 · Musical Building BlocksLesson 3 of 17About 6 minutes
What you’ll learnWhat musical relationship does Flat Side Logic reveal, and how can you recognise it?
The Rectangle · Lesson 3
6 | Flat Side Logic
A negative T value tells how many flats to take from the fixed flat order.
Lesson 6Application
1 · Choose a flat-side tonic
The keyboard shows all required flats in order and identifies the newest one.
Rectangle formula for flat keys
Flat order / left side
Bb → Eb → Ab → Db → Gb → Cb
Take the first flats indicated by the selected T value. Gb requires Cb as the 6th flat.
Keyboard visualization — active flats
Current selection
New flat added
Flats in order
How it works: Use the flat-side Rectangle value. Then add flats in order: Bb, Eb, Ab, Db, Gb, Cb.
Fork / odd natural values
−1 → +1 → +3 → +5
F, G, A, B increase by +2.
Chopsticks / even natural values
0 → +2 → +4
C, D, E increase by +2.