Three-line

Under the Helmholtz Octave Designation System, a name applied to the octave which extends from C 3 in the octave above the treble clef staff to B 3 in the second octave above the treble clef staff. The notes are indicated by lowercase letters with the superscript "3" ( c3, d 3, e 3, f 3, g 3, a 3, and b 3). This octave can also be designated with three hash marks (i.e. C''' ) or in the 6th octave under Acoustical Society of America system (i.e. C 6). The MIDI Octave Designation System has two versions, one where note 1 (8.176 Hz) is octave "0" making the Three-line octave the seventh octave (i.e. C7), and the other with note 1 (8.176 Hz) at octave "-2" making the Three-line octave the fifth octave (i.e. C5). The indication 8va (shown below) can be used to represent the same pitches without as many ledger lines.