Click on the chart and use the left and right arrow keys to walk the age bands, and the up and down arrow keys to move between the two sides and the balance between them. The pitch takes the size of a bar and the announcement names its side, which is how a sighted reader takes it in — length from the bar, side from which way it points. Press B for braille, T for text descriptions, and S to toggle sonification.
Without diverging: true the same chart is read as two
ordinary bar layers, which is the honest default: the sign then stays in
the announcement, where a reader can hear it.