When the updated tuning is being applied, the app can use one of the two strategies of what to do with the existing content of a score.
- It preserves the actual notes on the stave, but alters the fret numbers on the tablature.
- It preserves the tablature, but updates the pitches of the corresponding notes.
Transpose frets option of the Tuning tool specifies which strategy is to be used.
If the Transpose frets option is on, the existing pitches stay untouched, while the fret numbers are transposed.
The value by which the fret number is altered is calculated as the semitones difference between the note of this open string in the old tuning and in the new one. For example, the tuning is changed from E₂-A₂-D₃-G₃-B₃-E₄ to D♯₂-G♯₂-C♯₃-F♯₃-A♯₃-D♯₄. In this case, the fret numbers of the first string are raised by one because the number of the semitones between D♯₄ and E₄ is one.
With the Transpose frets option off, the fret numbers in the tablature don't change, as the pitches of the corresponding notes are redetermined by these fret numbers according to the new tuning.