Ernst Kurth describes in his book "Grundlagen des linearen Kontrapunkts" from 1917
moving tendencies of the pitches of chords. For example e in c e g tends to f and transforms
from the third to the base tone in a movement from c e g to c f a.
Motivated by the work of Kurth,
this app demonstrates a method to quantify the degree a key persists in the chord it is part of.

The keys are represented by colored chips which can be dragged.