Click a key to play it; the pitch played will be determined by a rough JI ratio between that key and the last key played. For example, if you played C, then G, that's a JI ratio of 3/2 with an error of about +2 cents, so that key will be detuned 2 cents. If you were then to play Bb, that's a ratio of 6/5 with an error if about +16 cents, so that key will not only be detuned by 16 cents, but by 18 cents, because that interval was based on the already-detuned G. This statistic of how much you have moved from normal tuning is shown on the top-left in cents. Click the "REDEFINE A RATIO" button to change a defined ratio. Input the key and the ratio and the calculator will automatically calculate and set the new ratio, rounding to the nearest cent.
The preset ratios are: 0) 1/1 "unison" 1) 16/15 "just diatonic semitone" 2) 10/9 "minor tone" 3) 6/5 "just minor third" 4) 5/4 "just major third" 5) 4/3 "just perfect fourth" 6) 36/25 "classic diminished fifth" 7) 3/2 "just perfect fifth" 8) 8/5 "just minor sixth" 9) 5/3 "just major sixth" 10) 16/9 "Pythagorean minor seventh" 11) 15/8 "just major seventh" 12) 2/1 "octave"
