Can magic mouth convey as a message a song (or at least something that resembles one)?
Its description states "...and recites the message in your voice and at the same volume you spoke".
A message that could be written as "nà, nananà, nà, nà, nà" could be "spoken" using appropriate volumes and tones for the individual words — that would be a melody. I mean, speech is a more complex thing than just "volume", since there is also the voice tone that varies frequencies.