[4candles]

The CD-Recordable FAQ (http://www.cdrfaq.org/faq07.html#S7-17) has the following to say about data/music blanks:

"Consumer" stand-alone audio CD recorders require special blanks. See section (5-12) for details. There is no difference in quality or composition between "data" blanks and "music" blanks, except for a flag that indicates which one it is. It's likely that "music" blanks are optimized for recording at 1x, since anything you record "live" is by definition recorded at 1x (though some dual-drive systems allow track copying at higher speeds).

You don't have to use "music" blanks to record music on a computer or on a "professional" stand-alone audio CD recorder. Nothing will prevent you from doing so, but there's no advantage to it.

The "music" blanks are more expensive than the "data" blanks because a portion of the price goes to the music industry. The specifics vary from country to country. In the USA, the money goes to the RIAA, which distributes it to artists who have navigated through a complicated application process.

Some manufacturers have on occasion marked low-quality data discs as being "for music", on the assumption that small errors will go unnoticed. Make sure that, if you need the special blanks, you're getting the right thing.

(Technically, there are actually three kinds of blanks: type 1a for CD-ROM or professional audio recording, type 1b for special-purpose applications like PhotoCD, and type 2 for unrestricted use. "Music" blanks are type 2, "data" blanks are type 1a.)

Some disc manufacturers label "music" blanks as "universal use", since they will work on anything.

So according to that description, it's possible that the problem is due to lower quality blanks, or blanks optimised for single speed writing that were written to at a higher speed.

If it was me, I would try the CDs in two or three different drives and if none of them work, contact the person who sent them to me and ask him/her to resend on different media. At the end of the day, it doesn't really matter why the discs don't work, just the fact that they don't.