Middle C and octaves

Key idea Middle C is C4, the C nearest the middle of the piano. The number after a note name is its octave, and it goes up by 1 each time you pass a C going up.

An 88-key piano has eight Cs. Find the group of two black keys near the middle; the white key immediately to its left is middle C (C4), the shared landmark for both hands and written music. Shorter keyboards cover different octave ranges, so use the C4 label or reference to identify the correct octave.

Octave numbers change at C, not at A. So the B just below middle C is B3, and the D just above it is D4.

What an octave is

Two nearest notes with the same name are an octave apart: 12 keys counting black keys. They sound alike, just higher or lower. That is why they share a name.