the pitch C4, frequency=261.6 hz, which is roughly in the middle of a piano keyboard and occupies the ledger line in the middle of a grand staff.
"Middle C" is the note that falls directly between the bass clef staff and the treble clef staff. "Middle C" is also the piano key that falls closest to the middle of all the other keys on a full-sized piano with eighty-eight keys.
The C nearest to the middle of the piano keyboard. This note is an important point of reference because it is on the ledger line between the treble and bass on the ground staff.
The note C in the middle of the Grand staff, and near the middle of the paino.
In Western music, the expression "middle C" refers to the note "C" or "Do" located exactly between the two staves of the grand staff, quoted as C4 in note-octave notation (also known as scientific pitch notation). It also tends to be to the middle of a keyboard, and it is near the top of the male vocal range and the bottom of the female vocal range.