My DS is not a great singer, but he loves all types of music. When he was younger, he would try and learn the theme songs to he favorite shows. He could get them after hearing them a few times. I realized at one point he would sing the words he knew and hum the tune when he did not know the words, adding more words each time until he had the whole song down.
We often have to sit in the driveway to hear the end of a song if it is one he likes as he sings along quietly to it (I think he knows he doesn't sing very well and so does it quietly.)
