What citation style are you using? MLA (the style most commonly used for humanities disciplines)? Do you need to make an in text citation or list of works cited? I've checked the MLA Handbook and an online source Diana Hackers Research & Documentation Online and it doesn't look like MLA has a specific rule for lyrics. I think you'd be OK to apply the rules for citing a verse, play or poem (See 19 under it-text citations) or a sound recording (see 42 under list of works cited).