Good thing for him then that Lucifer is about the fun. If ever there's a moment Istredd slips too much into thinking about processes and motion, that's when Lucifer distracts him, either with briefly taking over to spin them or a mental prod and a humorous trill.

Mmmmm... really popular musicians? He'd mentally share some rock music over their minds if he didn't think that surprise would actually trip Istredd up. Liked crazed-fan almost-cult following.

Which might make sense as to why Lucifer sought out the particular vessel, but there were several reasons at the time.