Abbreviation for quindicesima or "at the fifteenth." This indication is found above specific notes on a staff and indicates that those notes should be performed two octaves higher than written. This indication can be used with a dotted line that covers a series of notes to be performed at the fifteenth. The dotted line should end with a downstroke to indicate the end of the passage to be altered. The end of the passage can also be indicated by the term loco ("at place") or perform at the written pitch.
Although the indication of 8va is widely used, this indication is rarely used. When it is relatively easy for a performer to play one octave higher than the written notes, transposing two octaves higher is much more difficult.
It should also be noted that since an octave is eight notes and two octaves, being twice the interval, should be 16 notes. After careful examination, it becomes clear that the last note of the first octave is the same as the first note in the second octave, so there are only 15 notes in a two octave interval.