Mean Tone Scale

The next evolution from the Just Scale was an attempt to solve the problem of uneven perfect fifths, while maintaining the just major thirds.  This was accomplished at the expense of the Pythagorean perfect fifth and is called the Mean Tone Scale.  The idea is to keep all three major thirds: C to E, F to A and G to B at a 5:4 ratio, make all of the major seconds equal and then make the minor seconds so the math works out (i.e. everything fits in one octave.)