Hidden Music on Macbook Air

Hi,

Was synching the iPhone with Macbook to clear a song which wouldn't delete. Worked fine. However, when I now go to the 'Sync Music' option with 'Entire Musice Library' highlighted, it says abive '55 Songs'. I'm sure I don't have any files on the computer itself and there is nothing in the iTunes folder. Where are they lurking?

Thanks.

D