I don't think there's a command-line mp3 player that comes already
installed. If you use fink or darwinports there might be. but of course
you can run mac programs from the command line if you want to just open a
particular file from the command line.
For example:
open -a /Applications/iTunes.app music.mp3
or whatever the file is.
I guess what you would do depends on why you want it to run from the
command line.
You wouldn't get anything with "man mp3' anyway; to get a man page you
have to use the name of the program.
--
Cheryl
"Where your treasure is, there will your heart be also."