In the Go A.P.E. System we use one of three different temperament sequences to tune the temperament octave. That's what makes it so accurate. Traditional methods use the same sequence to tune all pianos, no matter what inharmonicity the piano has.
We determine that inharmonicity by aurally measuring the inharmonicity of the F3F4 and A3A4 octaves.
This allows us to tune these two octaves to a very high level, but the main reason we do this is to get the feedback on the octave scale - Small, Medium, or Large - which tells us which sequence will be the most accurate for this piano.
These two flow charts show how simple it is to determine each octave's inharmonicity.
The first chart is the simplest but the 2nd one shows what to do in some unique situations - when tuning a wide 4:2/narrow 6:3 produces a pure 4:2/pure 6:3, and when the pure 4:2/very narrow 6:3 doesn't sound better.
Basic Octave Tuning Flow Chart
Advanced Octave Tuning Flow Chart
Watch this demonstration:
