Tip: Since songs are always full of informal language, it's very common to find contractions and not full forms (e.g.: I'm, you're, it's, it'll, I'd, etc.). Be sure to use the contracted forms and not the full forms according to what you hear.
There is a case of contracted forms that you may need to use in conditional type 3. This is the case of WOULD followed by HAVE. The contractions could be WOULD'VE or, more informally, WOULDA.
Be sure you use the correct contraction to complete the lyrics.