The 'Produced notice' frame, in which the string must begin with a
year and a space character (making five characters), is intended for
the production copyright holder of the original sound, not the audio
file itself. The absence of this frame means only that the production
copyright information is unavailable or has been removed, and must
not be interpreted to mean that the audio is public domain. Every
time this field is displayed the field must be preceded with
"Produced " (P) " ", where (P) is one character showing a P in a
circle.
@author Eric Farng
@version $Revision: 1.4 $