Definition of middle C in English:

middle C

Pronunciation /ˈmidl sē/ /ˈmɪdl si/

noun

Music
  • The C near the middle of the piano keyboard, written on the first ledger line below the treble staff or the first ledger line above the bass staff.

    ‘It starts at the very beginning by introducing the treble clef and finding middle C on the keyboard and continues from there.’
    • ‘For example, the A above middle C on the piano is set to the standard value of 440 Hz, so the A an octave above that has a frequency of 880 Hz.’
    • ‘But when the first ladybug is on treble clef middle C, only an up arrow appears.’
    • ‘His splendid voice spans the low C of a true bass and the middle C of most tenors.’
    • ‘Diane brought Matt into the family room and introduced him to the middle C on the piano.’