Lt. Bob said:
...bands that play in stereo are wasting their time. All that happens is the people on the right just don't hear whatever's panned to the left. Stereo only works if you're sitting in the sweet spot.
I don't think is is quite true. For perfect stereo and all those wacky effects (even John Denver did it on the intro to "Country Road"!), the sweet spot is necessary.
For "stereo" in a more general sense of the term, as in soundstaging, etc, "sweet spots" are not as well defined (or at least far larger--does this make any sense?). Some arrangements need to be a panned at least a bit so everything isn't stepping on everything else. Sound fidelity issues aside, compare some old big band recordings in mono to something like "Afro-Cuban Jazz Moods" by Dizzy Gillespie and the Machito Orchestra. The Diz record would suffer in mono, IMHO-- there's too much rich-sounding stuff going on for one channel, drums over here, percussion here and there, horn sections on either side, Diz dead center--it's a super record. I love the old big band stuff too, and I do marvel at how they could record such large bands and have everyone in them be heard.
And for modern heavy-guitar bands, stereo is necessary (at least for those with two guitarists). A one-axe lead-in to the next riff after a rest would sound so crappy in mono--like the volume got cut or the master suffered a drop-out. Having that one axe off to the side (not 100%, mind you!), leaving acres of sonic spaciosness to be filled by the other axe, the bass, and the drums when they kick in at the end of the measure, is just so incredibly powerful. And it gives the producer a chance to have something resembling dynamics.
With the jazz and the heavy stuff, I find that you get a at least a sense of soundstaging as long as you're in the room with the receiver, sweet spot or not. Sort of like watching a band from off to the side instead of dead center front row.
All that being said, crappy four-track recordings sometimes get new life in mono, somehow. (Phase issues killing all the crappy excess frequencies?

)
Just a rambling 2 cents from a clue-impaired newbie.
