i was wondering about the same thing dan was. I already took a bunch of covers that I redid myself and put them on the internet. However, they are all classical covers and I don't think the Bach family is try to come after me. But let's say I did this with modern music. No one has ever paid for a copy of the songs, yet I put my name on them and list it as a cover of the original artist. Anyone that wants to hear it can download at will. Is there anyway the artists could prevent me from doing this? You might say no because I am not making any money off of it. But what if I did them so well that I became famous? Because of the cover songs, I could make a great deal off of my first original release. Would I owe anyone?
Actually you probably owe somebody right now. US copyright law provides for a compulsory license for recordings of such material. Basically if a musical piece has already been recorded then any other person can make a cover version without the author or copyright holder's permission by paying statutorily determined royalty rates. Whether you are "making any money" has nothing to do with this, as in fact it has almost nothing to do with any issue of copyright (except some limited types of fair use). If you didn't send a notice for the compulsory license then distributing the cover creates the potential for an action for copyright infringement (though the reality is that this won't much matter unless there's--surprise--money involved). There are limitations to a compulsory license such as the new version must be intended for public distribution but private use (so the license doesn't apply to commercials or film use) and there aren't supposed to be fundamental changes to the original (this is naturally a bit vague in practice). You can see details in the US code at Title 17, Chapter 1, section 115. Lang