MIDI numbering, the Helmholtz Pitch Notation System
and other octave numbering conventions
used in music and music notation

The following charts show four common pitch and octave numbering systems.
The pitch range in each chart is the same, but the notation appears on staves with different clefs.
The notation and pitch numbers are shown on a grand staff (treble clef and bass clef), then
on a treble clef, next on bass clef, and lastly on a staff that changes from bass to treble clef.
(The underlining is present merely to deliniate an octave)