multiple audio channels?

[don fisher]

Hello,

It would be useful to be able to watch a video in Firefox, pause it, and 
preview another video. Or pause it and listen to some music via 
rhythmbox. But it appears that the first application attaches the audio 
channel, and all other audio sources are blocked.

Is there any way to simulate the selector switch present on stereo 
receivers that allow selection of some arbitrary source, without 
shutting down the other sources? If so, how does one specify to 
realplayer or rythmbox which channel to use?

Some mixers allow definition of channels for recording, but I do not see 
similar capabilities for playback. I started to look at Jack, but that 
appears to be hitting a mouse with a sledge hammer:-)

Any references would be appreciated.

don