Piano: the Notes a Chart Never Prints

Pick a root and one of 24 types and see it as it lies on this reader's keyboard, every key numbered by degree. A number chart is a list of chords and bar counts; everything else that happens is somebody's decision, made in real time out of a map like this one.

The right hand takes the fill and the left keeps the written number sounding under it, so a piano reader hears every note of the scale against the chord the chart called rather than in place of it.

That silence is a feature. A chart that specified the notes would take an hour to write and would stop being readable at a count-off, which is the only thing it was ever for.