How do you get more songs on Wii Guitar Hero World Tour?

I have the Wii Guitar Hero World Tour, but cannot figure out how to get more songs. I know that on Rock Band as you play you earn more songs, but that does not seem to be happening to me on Guitar Hero. I tried entering a cheat code to get more songs, but that didn’t work either. I am stuck with the same songs that were on it when I bought it and I want more songs! Any help? Thanks