create_json.js

var fs = require('fs'),
	mmd = require('musicmetadata');

// Parser
var walk = function(dir, done) {
  var results = [];
  fs.readdir(dir, function(err, list) {
    if (err) return done(err);
    var i = 0;
    (function next() {
      var file = list[i++];
      if (!file) return done(null, results);
      file = dir + '/' + file;
      fs.stat(file, function(err, stat) {
        if (stat && stat.isDirectory()) {
          walk(file, function(err, res) {
            results = results.concat(res);
            next();
          });
        } else {
          results.push(file);
          next();
        }
      });
    })();
  });
};

var trackCount = 0,
	tracksLoaded = 0,
	data = {};

walk('./music', function(err, results) {
	trackCount = results.length;
	results.forEach(function(item) {
		var simpleTrackName = item.replace(/^.*\/|\.[^.]*$/g, ''),
			parser = new mmd(fs.createReadStream(item));
		parser.on('metadata', function(result) {
			data[simpleTrackName] = {
				title: result.title,
				artist: result.artist,
				album: result.album
			};
			console.log(tracksLoaded + '/' + trackCount);
			tracksLoaded++;
			if (trackCount == tracksLoaded) {
				console.log(JSON.stringify(data));
			}
		});
	});
});