I put some strings on my guitar that sound really tinny when in standard tuning. I dropped the tuning on all strings by 1 step down. It would probably be just right, if I could figure out how to tune it down just a half step But that's not the question.

The question is can you play guitar along with others playing a step above or below or do you have to play in the same key to sound in sync? I am pretty sure the answer is no, you all have to play in the same key.