He also has a system of musical tuning named after him (it isn't clear if it was developed by him), with the intervals being related in simple ratios to each other. It is often called just (or perfect) temperament, where things sound perfectly in-tune. However, it suffers problems in not being able to close the octave (a cycle of fifths should return back to the beginning, but it doesn't in this tuning system). Also, problematic was the fact that one key will be perfectly in tune, and every other key will have different shades of sounding horrific!