JHW - Why make CD-R's? Because reputable CD duplicators need evidence that copyright fees have been paid, (e.g. to MCPS in UK) and quantities are logged. For small quantites, a flat rate fee often suffices, but if you keep doing more copies, the fee may go up.

Making your own CD-R bypasses this, but illegally if there is any copyright song or music. And you may be amazed what is subject to copyright.

"Happy Birthday to you" is one example.

Wild Mountain Thyme is another, even though based on a 1797 song.
Certain people made a career of copyrighting traditional songs!
And there is no definitive source of public domain songs.