Previous: Logarithmic Units, Up: Units  12.6 Musical Notes  Calc
can convert between musical notes and their associated
frequencies. Notes can be given using either scientific pitch
notation or midi numbers. Since these note systems are basically
logarithmic scales, Calc uses the l prefix for functions
operating on notes.  Scientific pitch notation refers to a note
by giving a letter A through G, possibly followed by a flat or
sharp) with a subscript indicating an octave number. Each octave
starts with C and ends with B and the octave numbered 0 was
chosen to correspond to the lowest audible frequency. Using this
system, middle C (about 261.625 Hz) corresponds to the note ‘C’
in octave 4 and is denoted ‘C_4’. Any frequency can be described
by giving a note plus an offset in cents (where a cent is a
ratio of frequencies so that a semitone consists of 100 cents).
The midi note number system assigns numbers to notes so that
‘C_(-1)’ corresponds to the midi note number 0 and ‘G_9’
corresponds to the midi note nu