Get pitch class of a note or midi number

Get the pitch class of a note:
``js`
var pc = require('pitch-class')
pc('a4') // => 'A'
pc('fx3') // => 'F##'
It works with midi numbers too:
`js`
pc(57) // => 'A'
This is part of tonal:
`js``
tonal.pitchClass('bb2') // => 'Bb'
MIT License