Figure 7.4.4. Using voice leading to calculate distances between keys. (a) For major keys, the distances are simply the voice leading distances between the relevant diatonic collections. (b) For distances between major and minor, we calculate the size of the voice leadings from the major scale to each minor scale, and take the average. Here, the average distance between C major and the three A minor scales is 1. (c) For minor scales, we take the average of the three voice leadings in the most efficient pairing of the scales in one key with those in the other. Here, the average distance for the best pairing between A minor and E minor scales is two.