Numbered musical notation and so on. Dashes after a note lengthen it, each dash by the length of a quarter note. A dot after the plain or underlined note works increases its length by half, and two dots by three quarters. The underline, along with its joining, are analogous to the number of flags and beaming in standard notation. So are dotted notes. But the analogue stops at notes worth three quarter notes and beyond, where dashes are used instead. The number "0" represents the musical rest. The rules for length is similar to that of the note, except that it is customary
Musical note but has double its frequency. The name octave is also used to indicate the span between a note and another with double frequency. To differentiate two notes that have the same pitch class but fall into different octaves, the system of scientific pitch notation combines a letter name with an Arabic numeral designating a specific octave. For example, the now-standard tuning pitch for most Western music, 440 Hz, is named a′ or A4. There are two formal systems to define each note and octave, the Helmholtz pitch notation and the scientific pitch notation. Letter names are modified by the accidentals.