Calculate a modular scale
Idea from http://www.modularscale.com/
npm install modularscale
var ms = require('modularscale');
// Defaults to using golden ratio
ms(1);
// --> 1.618
// Set desired ratio
ms(1, "minor second");
// --> 1.066
// See modularscale.com for the full list of preset ratios.
// You can also pass it any ratio you'd like.