Exact middle (or 2/3, 3/4, 5/4 etc.)

The exact middle (as well as the 2/3, 3/4, 4/5) point of the string varies according to the position of the pedals. The pedal mechanism shortens the strings, and therefore there are three harmonic points on each string. There is one harmonic point for the flat, one for the natural, and one for the sharp pedal position. The distance between these three points is greater where the strings are longer.

Octave harmonic on one string with three different pedal positions.