Polyphony

Forty glaciers, each drawn as three points that circle one another: violet for snow cover, cyan for snow line and white for fragmentation. When the three measures agree, the points stay close and the lines are cool and faint. When they diverge, the points move apart and the lines turn red.

40 glaciers chosen for their spread and size among the 1,500 largest of 20,150. For each one, three yearly measures brought to a common health scale from 0% to 100%: snow cover, snow line and fragmentation, the last two inverted because a lower snow line and less fragmentation mean a healthier glacier.

Sound and image come from the same list of 7,621 notes.

Each glacier has a home note and three voices an octave apart: a pad, a pluck and a bell. A voice leaves its octave in proportion to how much its measure differs from the average of the three, so you hear pure octaves when they agree and clashing notes when they diverge.