From my experience playing in class I think each of us knows the lead while playing at home but we're confronted with a different situation when playing together. I guess we all have our individual quirks as far as what throws us off when performing together and mine is when I can't hear a lead when it's played, I'm assuming the rythmn section is waiting and sitting on a chord until a lead is taken only to find out someone is playing a lead!
That's when I lose my concept of where the rythmn section is:unsure: . On the other hand, not being a solid rythmn player anyway I make the chord changes at the wrong time while listening to the lead(who's off on the wrong beat)
. I have to work on my keeping a solid rythmn but, it's difficult when I can't hear a lead or when the lead takes off on it's own agenda. I'm working on focus and fun.