I've actually spoken to a lot of guitar techs' and such and they've told me that in a lot of cases, like Guns n Roses, they tune down a half a step because Axle will sing flat a lot. So if you tune your guitar flat while your singer sings flat, he'll be in key.
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BadHorsie, holdin' it down like Gravity!
Ain't nothin' but a Gear thang, baby!