Given a set of notes, which may be either a chord or a sequence of notes such as an arpeggio, this section gives a method and variations for determining the Fundamental note of that set. The fundamental note has a frequency that divides exactly into the frequencies of all the notes in the set. The procedure under Ratio Note Finder above yields both the fundamental note, and the ratios of the notes in the chord. These give the exact ratios to be used when playing the chord. The frequency of the fundamental note is not as straight forward as finding the ratios of the notes in a chord.
Various schemes are possible, and each has advantages and disadvantages.
Use the equitempered scale for the fundamental frequencies. It is also easy to predict. Base the basic scale frequencies. This depends on the key being declared beforehand. The method is technically more correct than 1, but declaring the key may be a nuisance.