Combination tone

Since a fifth corresponds to a frequency ratio of 2:3, the higher tone and its harmonics would then be

Sum and difference tones are thought to be caused sometimes by the non-linearity of the inner ear.

This causes intermodulation distortion of the various frequencies which enter the ear.

However, experiments show evidence that even when using headphones providing a single pure tone to each ear separately, listeners may still hear a difference tone[citation needed].

Since the peculiar non-linear physics of the ear doesn't come into play in this case, it is thought that this must be a separate, neural phenomenon.

A resultant tone is "produced when any two loud and sustained musical sounds are heard at the same time.

Using a resultant tone for such low pitches reduces the cost and space factor, but does not sound as full as a true 32' pipe.

The effect can be enhanced by using further ranks in the harmonic series of the desired resultant tone.

It can vary from highly effective to disappointing depending on several factors, primarily the skill of the organ voicer, and the acoustics of the room the instrument is installed in.

It is possible to produce a melody with resultant tones from multiple harmonics played by two or more instruments.