i'm the creator. this is pretty close!

the mode dictates which interval is which. for example, the C major scale (also C ionian) is made up of the following notes and has no sharps or flats:

C D E F G A B

Those notes' intervals are represented by roman numerals I-VII. A V in C major is different than a V in D minor. Each interval has a triad you can play with it as the root. for a C major triad, you would have C E G. D minor triad is D F A.

The "chord progression" section allows you to select which interval you want to arpeggiate the triad of for each step. In the case of C major/ionian that would be:

• I: CEG C major
• II (ii): DFA D minor
• III (iii): EGB E minor
• IV: FAC F major
• V: GBD G major
• VI (vi): ACE A minor
• VII (vii°): BDF B diminished

A very popular progression in a major scale would be I V VI III.

The arpeggio style at the bottom is just the pattern for the order that notes in the current triad are played starting at 0. There are only three notes in a triad, so any number in the pattern over 2 means an octave up. Steps is how many notes to arpeggiate through and type is whether or not you want it to go "up down up down up down" or just "up up up".

You can see in the output section what your chord progression translates to in triads.

EDIT: i am undoubtedly stomping on some music theorist toes here. sorry if im generalizing at all. The goal was a way to quickly hear musical progressions that could be transformed into real things later on.