**Ramsay**

If it be asked why no more primes than 2, 3, and 5 are admitted into musical ratios, one reason is that consonances whose vibrations are in ratios whose terms involve 7, 11, 13, *etc.*, would be less simple and harmonious than those whose terms involve the lesser primes only. Another reason is this - as perfect fifths and other intervals resulting from the number 3 make the schism of a comma with **perfect thirds** and other intervals resulting from the number 5, so intervals resulting from the numbers 7, 11, 13, *etc.*, would make other schisms with both those kinds of intervals. [Scientific Basis and Build of Music, page 75]

See Also