Under the Helmholtz Octave Designation System, a name applied to the octave which extends from C5 in the third octave above the treble clef staff to B5 in the fourth octave above the treble clef staff. The notes are indicated by lowercase letters with the superscript "5" (c5, d5, e5, f5, g5, a5, and b5).

This octave can also be designated with five hash marks (i.e. C''''') or in the 8th octave under Acoustical Society of America system (i.e. C8). The MIDI Octave Designation System has two versions, one where note 1 (8.176 Hz) is octave "0" making the Five-line octave the ninth octave (i.e. C9), and the other with note 1 (8.176 Hz) at octave "-2" making the Five-line octave the seventh octave (i.e. C7).

The indications 8va and 15ma (shown below) can be used to represent the same pitches without as many ledger lines. The indication 15ma is rarely used today.


Play Five-line Octave Example (MIDI file format)

More about octave designations; More about pitch.
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