This article is from the CD-Recordable FAQ, by Andy McFadden (email@example.com) with numerous contributions by others.
The CD-Rs required by "consumer" stand-alone audio recorders (section
(5-12)) are more expensive than the standard "data" CD-Rs. Converting a
standard blank into a consumer-audio blank is like converting lead to gold,
in two ways: it would save a lot of money, and it's impossible.
CD-Rs have some information pressed into them that cannot be altered. One
such tidbit is the Disc Application Flag, which tells the recorder what
sort of blank you've inserted.
There are ways to trick certain recorders into accepting other kinds of
blanks (some of which are mentioned in section (5-12)), but there is no
way to disguise the blank itself.
(For the nit-pickers: apparently some experiments with nuclear reactors and
particle accelerators have actually resulted in conversion of lead to gold.
It is unlikely that placing a "data" CD-R in a particle accelerator will
do anything useful, however.)