Zoom

// zoom in / out factor
            float zoominFactor = 1 / 12f;

This provides zoom ratios of 1/2, 2/3, 3/4, 5/6, 1/1, 7/6, 5/4, 4/3, 3/2
These ratios keep artifacts to a minimum. There are still a few oddball sizes not mentioned but they keep the zoom changing by a fixed amount. 1/12 is a better value than 1/20 (0.05f). This is consistent with the reason an octave contains 12 notes.
