Measuring the piano’s A4 Numbers
The “A4 numbers” are the locations of the 2nd, 4th, and 8th partials of A4 when A4 is tuned to A440 (1st Partial).
Mapping pianos for tuning.
Mapping (and tuning) notes during the mapping process is the equivalent of setting the temperament in aural-only tuning.
Mapping A4
It all begins with A4. A4 is tuned to A440 which on a well calibrated SAT will be (A4 @ 0.0). So pick a string of A4, and tune it to stop the lights.
The “4th” A4 Number
Measuring the “4th” A4 Number After determining the A4 numbers, the next step is to locate the “4th” A4 number. To measure the “4th” A4 number, technicians focus on the 2nd partial of A4. This “4th A4” value represents the width of the A3/A4 2:1 interval after A3 has been tuned as a pure 4:2…