tunefully       
adverb uk/ˈtʃuːn.fəl.i/ us/ˈtuːn.fəl.i/
 音调优美地,声音悦耳地
in a way that has a pleasant tune
  The song was sung tunefully to the accompaniment of a guitar. 这首歌是在吉他伴奏下优美地唱出来的。 
 The opera is a tunefully entertaining piece of theatre. 这个歌剧是一部曲调优美、赏心怡情的剧作。 
 See: tuneful
 - More examples
 - The aim of the game is to sing your heart out as tunefully as possible.
 - "Can't sing," he said, as he strummed his guitar quite tunefully.
 - The baby coos tunefully throughout my visit.