 Pythagorean tuning may be regarded as a "three-limit" tuning system, because the ratios can be expressed as a product of integer powers of only whole numbers less than or equal to 3.A twelve-tone scale can also be created by compounding harmonics up to the fifth.Namely, by multiplying the frequency of a given reference note (the base note) by powers of 2, 3, or 5, or a combination of them.