One-line octave
Octave range from c' to b'; contains standard concert pitch a'.
What it means
The one-line octave spans the pitch range from c' to b' and, with a', contains the internationally standardised concert pitch to which orchestras and instruments are tuned. It lies one octave above the small octave and marks, for many instruments and voices, the middle, comfortably reachable range.
In the notation
In the German naming tradition, the one-line octave is marked by a single small stroke after the letter, c' and so on, corresponding to C4 in scientific pitch notation (middle C). In the treble clef, its notes mostly lie on and above the staff lines; in the bass clef, they lie above the staff with ledger lines.
Musical use
The one-line octave forms, for many melody instruments and the human speaking voice, the central, most frequently used range, where tone and response are especially balanced. Its a', today usually fixed at 440 or 442 hertz, serves as the shared reference point to which all instruments of an ensemble tune.
The one-line octave should be distinguished from the small octave, one octave below it and marked with lower-case, unmarked letters, and from the two-line octave, one octave above it. The German octave-naming system continues upward with the two-line, three-line, and four-line octaves.
Performance practice
Use the a' of the one-line octave as a reliable reference point when tuning your instrument, for instance with a tuning fork or an electronic tuner. In singing and on many melody instruments, the one-line octave usually lies in an especially comfortable, well-projecting range, which makes it a good place to begin exercises in tone production and intonation before moving to higher or lower registers.