The PC3K manual states, “Intonation Key (Int. Key): This sets the tonic, or base note from which the currently selected intonation map calculates its intervals. If you select G as the intonation key, for example, and the intonation map you select tunes the minor 2nd down by 50 cents, the G# will be a quartertone flat relative to equal intonation. If you change the intonation key to D, the D# will be a quarter tone flat. If you use nonstandard intonations, you’ll want to set Int. Key to the key you’re playing in. If the Intonation Key parameter is set to Equal, changing the Int. Key has no effect” (Kurzweil).
The intervallic tuning relationships of the keyboard template in the first section stays the same when using the Intonation Key parameter. Yet, the tonic of the intonation map can be easily changed.
This powerful tool enables the PC3K owner to shift keys, progressing around the circle of fifths. It gives easy access to all 24 major and minor keys.
If a second person operates the keyboard’s touchpad, it gives you the capability to change the Intonation Key during live performance. This person functions as a sort of temperament conductor. Consequently, Int. Key makes it feasible for Supplemented Equal Temperament to exceed the modulation limitations of the meantone tuning that Mozart used.
This shows that the chords in Supplemented Equal Temperament work well when used with the PC3K keyboard.