GarageBand on a Mac is perfect. You’re out of luck on Windows in the “free” category unless you can put up with Audacity. If you want to get serious about making music, consider scheduling some time at a local studio for a couple hundred dollars.
@Vortico I’m not sure. Its a weird al type idea I want to play with… so I need to download a song and put my own lyrics in… I guess it’ll all be on a microphone.
I like Audacity. I tried a number of free programs and it came out on top for my uses – recording real instruments/vocals and then cutting, changing tempo or pitch, etc. Not sure how easy it would be for what you describe, though.