That's probably the first picture of all four of us where we're doing something besides playing music!
At one point I became so involved with the process that I started to feel that I was the master, singing the refrain from this song to myself as we worked. Obviously I was the master of the studio, though, not of the gym.
Listening to the finished product, I'm struck both by how big the improvement was over what we came in with, and how different the bass sounds with a pick than it does with your fingers. The songs that I play bass on have a really deep dub tone, but the songs that Dave plays bass on have this punchy rock tone. I think the mastering process really brought those differences out.