A tiny (188 bytes) function to get the frequency of a midi note number:
var freq = require('midi-freq')(440)
freq(69) // => 440It uses an equal tempered scale. Basically it's just: Math.pow(2, (midi - 69) / 12) * tuning with a couple of goodies.
Get the frequency of a midi note with the custom tuning. If not specified, is 440Hz by default.
Get the frequency:
// 69 is note A4
var freq = require('midi-freq')
freq(440, 69) // => 440
freq(null, 69) // => 440
freq(444, 69) /// => 444
// 57 is note A3
freq(null, 57) // => 220
freq(444, 57) // => 222Normally you use the same tuning for all your app. You can partially applied the function:
var freq = require('midi-freq')(444)
// the freq function uses 444 as custom tuning
freq(57) // => 222MIT License