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 B, 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.
