Modern versions the instant messenger client Pidgin use gstreamers for their sound management. Sometimes you need to operate without gstreamers present on your system. But you still want sound though.
Here's a quick solution I've used in years passed. Go to Preferences -> Sounds -> Select "Method" and choose "Command". This will enable the input area with the label "Sou/nd command (%s for filename)". Into this box put this command:
That passes the sound from Pidgin to ALSA, which is supported on all modern Linux distributions and is also supported with backwards compatibility by PulseAudio.