The use of harmonics in astrology is quite old and was practiced to a limited extent in ancient India. Today, thanks to the use of computers, determining harmonics, a numerical relationship between aspects, has become easier, so the use of harmonics in astrological interpretation has become more popular.

Harmonic charts multiply the positions of planets by a number, resulting in the planets appearing at new positions. Generally, the number is from 1—12, although theoretically other numbers (up to 360) could be used. Harmonic charts are most often used to add specialized information to interpretations.