The shapes produced by using Steadman space as a filter for interpretting an incoming note stream can give us a lot of information about the harmonic nature of the notes being played. Basic to any interpretation of harmony is an awareness of the underlying key centre that the harmony is built from. Within mean tone harmonic space the frequencies of the incoming notes would naturally point to particular harmonic centres because they are derived from such root frequencies. In equally tempered space however this information is lost and we are only left with statistical reasoning about keys.
Every key has a unique combination of triads that can be built upon the degrees of its scale. For instance C major is composed of the triads: C major, D minor, E minor, F major, G major, A minor and B diminished. The following table shows how major and minor key triad distributions differ from each other.
If we keep statistical information about the combinations of triads which have been percieved then that can use that data to determine the statistical likelyhood of being in a particular key. Once we have established a key centre we can use this data to follow modulations into other keys.