你这句句子还缺少成份.help可以有好几种表示帮助做某事的搭配.
一种是help sb. (to) do sth. 所以你的句子里还缺少了sth.的部分,补充完整应该是Can you help me sing a song?
还有一种是help with sth. 帮做(某事),如果你的句子要改写成这样的形式就是Can you help with the singing?