 While the expression "Middle C" is generally clear across instruments and clefs, some musicians naturally use the term to refer to the C note in the middle of their specific instrument's range.C4 may be called "Low C" by someone playing a Western concert flute, which has a higher and narrower playing range than the piano, while C5 (523.251 Hz) would be Middle C. This technically inaccurate practice has led some pedagogues to encourage standardizing on C4 as the definitive Middle C in instructional materials across all instruments.On the Grand Staff, middle-C is notated with a ledger line above the top line of the bass staff or below the bottom line of the treble staff.