[LAU] How do you make a sound in both speakers at once, but not stereo

[Bearcat M. Sandor]

Hey folks,

I'm not an audio engineer and i don't even play one on TV. I am a music 
lover/audiophile who wants to learn about engineering so bear with me here. 

I understand that when you hear something in the center of your sound stage 
it's because the sound is equally loud in both channels and in phase.

If you hear it spread evenly across the sound stage or even "everywhere in 
front of you" the sound is equal in both channels and out of phase.

I heard a recording the other day where a singer was equally loud in both 
channels, but she was not center stage. Instead there was one of her in each 
channel.

How is that done? Thank you.

Bearcat M. Sandor