Back to the main topic:
"A friend told me that the music would be clearer if you burn at a slower speed"
This is simply not true. Whether you burn at 24x or 2x, the clarity of the music is going to be the same.
However, it's quite possible that your "friend" may have meant to use a different word other than "clearer". Burning at a slower speed may improve compatibility on older CD players, when trying to playback. Older CD players, as I have found, sometimes will not work with CD's that were burnt at speeds higher than 4x or 8x.
But as you have stated it, the idea is simply not true.
~cdogg
"The secret to creativity is knowing how to hide your sources."
- A. Einstein