gistfile1.js

var performers;

performers = {};

async.parallel([
  function(callback) {
    return conductor.find({}, function(err, result) {
      performers.conductor = result;
      return callback(err);
    });
  }, function(callback) {
    return soloist.find({}, function(err, result) {
      performers.soloist = result;
      return callback(err);
    });
  }, function(callback) {
    return orchestra.find({}, function(err, result) {
      performers.orchestra = result;
      return callback(err);
    });
  }, function(callback) {
    return chamber.find({}, function(err, result) {
      performers.chamber = result;
      return callback(err);
    });
  }
], function(err) {
  return res.json(performers);
});

awesome, thanks for this