harmonic method

Frequency harmonic(
  1. int index
)

The harmonic at index from this Frequency, including negative values as part of the undertone series.

Example:

const Frequency(220).harmonic(1) == const Frequency(440)
const Frequency(880).harmonic(-3) == const Frequency(220)

Note.c.inOctave(1).frequency().harmonic(3).closestPitch()
  == Note.e.inOctave(3) - const Cent(14)

Implementation

Frequency harmonic(int index) => Frequency(
      index.isNegative ? hertz / (index.abs() + 1) : hertz * (index + 1),
    );