PulseAudio depends on a dbus system daemon, make sure its enabled.

# xbps-install -S alsa-utils pulseaudio
# ln -s /etc/sv/dbus /var/service/

For applications which use ALSA directly and don't support PulseAudio, the alsa-plugins-pulseaudiopackage can be installed to make them use PulseAudio through ALSA.

# xbps-install -S alsa-plugins-pulseaudio

The PulseAudio package comes with a services file, which is not necessary in most setups and the PulseAudio maintainers discourage using a system-wide setup. Instead, PulseAudio will automatically start when needed.

There are different methods that work with PulseAudio to allow access to the audio devices, the simplest one is to just the audio group alternatively you can use a session manager, like elogind or ConsoleKit2.