Octaves

Octave of a pitch

Octaves are identified with various naming systems. Among the most common are the scientific, Helmholtz, organ pipe, and MIDI note systems. In scientific pitch notation, a specific octave is indicated by a numerical subscript number after note name. In this notation, middle C is C₄, because of the note's position as the fourth C key on a standard 88-key piano keyboard, while the C an octave higher is C₅.