I play at a weekly jam where I usually don't know the songs let alone the chord progressions. I am told the key and any really funky chords but rely almost totally on listening. The leader is very cool about muffed changes, so it goes well. I am used to reading music, so my ear training was very weak. If you ever have a chance to do this, I highly recommend it. For the first three sessions it was just two of us: guitar/vocals and bass. For the fourth jam, two other guitars showed up. All are fairly accomplished musicians. I am by far the least accomplished of the group, and everybody knows it. So we do some songs, some work and some don't. Sometimes the others know the song and the volume goes way up But I am really struggling on some songs, I just cannot hear the chords. The chord will sound right compared to the others, but not feel right. It slowly dawned on me that when the others don't know the song they are following me. So if I say drop to B when I am supposed to stay in E, the other guitars will follow and the three of us drown out the leader, who is playing the correct chord. It seems that the guitarists are so used to falling back on the bassist, they do so even when it should be fairly obvious that they shouldn't.