According to Jorge Almeida:
# I have version 2.5.0-1. There is no /usr/bin/audacious2 anymore. I
# don't know whether it's a different package or just a different name.
It's a newer version of the same package. It seems that there has been a
lot of development of Audacious between 2.4 and 2.5.
# Anyway, I suspect alsa problems, dating from the same upgrading, 2
# days ago or so. I remember seeing some useless alsa message that
# shouldn't be there if all went well. pacman -Syy seemed to clean up
# things, but it didn't. I just checked that xmms also doesn't work
# anymore.
I have just completed a rather large upgrade which, in addition to
Audacious, brought a shiny new kernel and some video package upgrades.
After rebooting the computer due to the kernel upgrade, I have noticed
no negative impact on performance, and all my sound works. As for
Audacious, I'm having a few hiccups with the new version, but it is
playing sound. The problems I'm having appear to be related to the
global hotkey plugin and an error message that indicates that Audacious
is already running when it in fact is not, rather than playback. A
possible difference may be the fact that I have pulseaudio installed,
whereas you may not, although pulseaudio shouldn't cause sound to work
if it won't play without it.
~Kyle