If you're making a CD you will need a licence from MCPS. That will certainly cover Ewan McColl songs, and many other modern songs. MCPS will then pay the rights holders. If you a covering a song by someone who is not a member of MCPS (or a similar rights organisation) then you will have to try to contact them directly for permission. There is no licence fee for trad material (provided you are not copying someone's copyright arrangement).