Sound from multiple sources?

How is it possible to set up my installation so that I can get sound from more than one source at a time? Currently if I run a Youtube video for example, I cannot then use Spotify. I get a “problem with your soundcard error” from Spotify. However, if I open Spotify first and then try Youtube there is no sound on Youtube. Simply shutting down one program does not seem to give the other access to the soundcard, this often requires a restart. Clearly this is not practical.

It must be possible to set up my sound so that the sound card can be used by more than one application per start up. Can anyone help please?

I’m running OpenSUSE 11.1 with the GNOME desktop.