If a shotgun must be used for stereo recording, M/S is greatly preferred. [snip]
But M/S at least lets you aim the shotgun at the center of the sound source, and get as much of it as possible into the pickup angle of the one microphone, without much if any off-axis pickup of direct sound sources.
Here's an alternate option which I believe will be superior for music recording from farther back in an outdoor situation-
Keep the single, directly forward facing shotgun orientation and instead of M/S with a 'side' figure-8 mic, substitute two spaced omnis. Need to either record all three channels seperately or mix them to 2-channel on the fly (left omni hard-panned left, right omni hard-panned right, shotgun panned to center).
I always thought this would be the way to go back in the day with the Nakamichi 3-mic sets which came with a 3-channel mixer and I suspect would be superior to the once common 3-mic outdoor Grateful Dead taper setup of two PAS shotguns + one center omni, for all the reasons DSatz mentions plus a few others. I'm mostly advocating this as 'better' because I prefer spaced omnis over M/S at a distance, and because like M/S it uses the shotgun appropriately (pointed the right direction, no phase-interaction problems with two of them, near-spaced). However it is certainly not limited to a shotgun. Using a supercardioid or cardioid for the center mic is the way I do it. Although I haven't used a shotgun for the center mic in this way, I think this is likely to be the best way to use one for music recording at a distance while limiting the problematic attributes of the pattern, providing clarity from the centrally located, directly forward-facing directional mic without phase interaction problems with another shotgun, or with the omnis since they are spaced far enough to either side of the shotgun-mic.
Several benefits of mixing a single forward facing shotgun with two omnis instead of running it M/S with a figure-8:
>Solid bass from the omnis,
>The 'big & open' spaced omnis sound,
>The omnis tend to ‘cover’ the shortcomings of the shotgun and vice-versa.
>Some 'antenna array' directionality from having three mics in a line (something of a relative to Tony >Falkner's 4-mic 'phased array' technique [not to be confused with his several decades older parallel 8's setup most think of when they hear the term 'phased array'])
It’s also an improvement over straight 2-channel spaced omnis-
>Increased articulation, clarity and reach,
>No problem with any wide A-B 'hole in the middle'.
>Both sharper imaging and increased envelopment.
One challenge is getting the omnis optimally wide using a single stand. As many of you know, I do that by using very light weight miniature omnis mounted on long telescoping arms but most tapers would need either multiple stands or to clamp the omnis to neighboring stands or along a railing.
I haven't done this with a shotgun in the center, but it is currently my favorite setup for outdoor material using a cardioid or supercardioid in the center. I just returned from running the 2meter spaced mini omnis with a center supercard at a 4-day outdoor festival over the past weekend. I did not intend this rig for use inside, but I also ran it FOB in the indoor music hall for a few sets, which I will need to listen to determine how well the wide spaced omnis worked from upfront indoors, in some ways that application was the opposite of what this was designed for, and assuming it worked well I think that will help establish it’s general flexibility.
The setup is much more forgiving and flexible overall than I though it would be, and as mentioned above, I think it would help manage some of the shotgun issues to get the best result possible given the other situational constraints.