Well I mean, when they want to demonstrate the importance of tones in Chinese, they usually give examples like, "Depending on tones, the sentence "Shing ying wei ni bao" can mean "I will love you until my death", or it can mean "The green monkey has stuck between the boughs" " (this example is just from my head, but you know it's like this). So, is it easy to understand the singer if he sings the song in wrong tones?