Good summation Craig. The only thing I'd add is the importance of the Performance playing the instrument well, and the emotional content of the individual parts. Like any live performance where a well rehearsed band uses varying amounts of energy dynamically as individuals and as a team effort, it is critical to tap into that same same kind of emotional energy when tracking in a studio.
In a solo project, this can be much more difficult because you may not have the other players there to follow the dynamic lead set down as a team. Control over this emotional expression as you perform trackin