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 number (and 69 is the number of semitones between C (note 0) and A). And in the opposite direction, to obtain the frequency from a MIDI note "p", the formula is defined as: For notes in an A440 equal temperament, this formula delivers the standard MIDI note number ("p"). Any other frequencies fill the space between the whole numbers evenly. This lets MIDI instruments be tuned accurately in any microtuning scale, including non-western traditional tunings. Music notation systems have used letters of the alphabet for centuries. The 6th-century philosopher Boethius is known to have used the first fourteen letters of