Kerplunk's right - nothing wrong with his memory this morning!. The minus sign in 'CD-R' isn't a minus, it's a hyphen, as in 'Compact Disc - Recordable'.
The + and - for DVDs are different, describing two different recording methods.
I have always used imation CD-R 700MB - 80min (obtained from Morrison's supermarket) for all my Music, Data, & Photo they also say they will do Video as well but I have not tried that.
You can also buy special music discs but these are more expensive, and I don't think you would notice much difference unless you are a complete music buff.
If you want the files to play in a CD player then use a CD-r.
If you want to play them in a dvd player that supports mp3 or want to move them to another computer then you can use either DVD or CD and burn them as data (MP3).
Obviously you must have a DVD burner to burn DVD's though.