I'm afraid that the only answer I can give is 'poetic licence'. It is 'non standard' grammar, presumably used because it 'sounds better'.

It is only do because this is a song, and the song writer wants to use this in his lyrics. It is not correct English. Often song writers, book athours and other creative writers will do this, they change things to make them sound different, better, unusual, strange, sad, bad etc. just to suit the mood.

G. Moe: It would be a mistake to think that songwriters are concerned with proper grammar, because they are not. Let me give one example to you, which shows, as Su.Ki advises, "poetic license". http://www.italki.com/entry/466227 (the use of "gonna" instead of "going to") This is one difficulty with songs as English study material. Songs are great to get a student speaking with confidence, and to some extent, writing with confidence. Still, the use of slang and idiomatic expressions must be recognized when they appear. Students do not want to copy all the patters of "spoken English" as a model for their "written English". There is a fancy term to know. It is "colloquialism". It refers to what people actually speak, regardless of whether or not it is "proper". .