[alsa-devel] explicit commandline control of speakers vs headphone output

[Eric Holstege]

It appears that when I have a headphone plugged in, the speakers are 
automatically disabled and the output sound is sent to the headphone.

However, I want to explicitly control (e.g. via a script or commandline 
- not a GUI) whether the sound from an (arbitrary) application is going 
to the speakers or to the headphone even when the headphone is plugged in.
(When I say "arbitrary application" that means I can't alter the code of 
the application itself).

Is this possible?

(I have heard that ALSA mutes the speakers when it detects plugged-in 
headphones. Is switching between them as simple as using e.g. amixer(1) 
to unmute the speakers and mute the headphones and vice versa, or is 
there more to it.)