True Modal Mapping
AutoTonic's clever modal mapping is based on just two components: 1) TONIC and 2) SCALE. It's the combination of these two settings which is capable to define any harmonic context existing in western tonal music. And basically, they're not very hard to understand at all …
By its nature, the 'Tonic Modifier' allows only one exclusive selection to be active at the same time. Here gets defined where the Tonic (colloquially often 'ROOT' note) sits, or, in other words: which 'key' the scale sequence output is be based on. Even when there are no intervals selected in the 'Scale Modifier' the 'Tonic Modifier' will always remain active and build the fundament for the output mapping …
The Tonic Modifier can be also considered as a 'direct' transposition method, where all of the harmonic context gets shifted the same amount of semitones up or down, depending on the selected tonic note height (C,C#,D,D#,E,F,F#,G,G#,A,A#,B). This kind of transposition technique can be also found on most modern electric pianos, often called 'Pitch' or '+/- Tune' etc,
So while the Tonic Modifier just pitches the playing up or down, linearly, the Scale Modifier instead – by excluding/including desired intervals – allows of defining the relative distances between each appearing note. Here's a visual reference, how C-Ionian (often "C Major" called) looks like in AutoTonic:
But, where it really gets interesting is when modifying these interval patterns in the 'Scale Modifier' by the use of their binary character. Because any of these intervals (11 available intervals without the Tonic) can be either toggled ON or OFF – so every potential permutation/pattern is feasible here.
Where other note transposers are often limited by using only 7-note respectively 5-note based mappings (hepta- and pentatonics), AutoTonic goes far beyond allowing you to choose literally ANY count of intervals per octave!
The visual concept of this Scale Modifier is – by the way – based on a left-to-right sequence where each following step describes the next higher interval (P1,m2,M2,m3,M3,P4,△,P5,m6,M6,m7,M7).
What's so important to understand here: it's THE COMBINATION of these two modifiers that is capable to define all the characteristics of any mapping which results on the white keys of your MIDI keyboard.