function hasSong(author, callback) {
  // Represent a async data fetch
  setTimeout(function() {
    callback(author === 'BestAuthor');
  }, 100)
}

function hasSongMessage(hasSong, callback) {
  setTimeout(function() {
  // Represent getting async message based on parameter
  if (hasSong) {
    callback('Has song');
  } else {
    callback('No song');
  }
  }, 100);
}