Much disputed! The engineers and piano tuner/designers of "TuneLab", "Verituner," "Sanderson Accutuner" etc etc--all high end piano-tuning programs tell you, basically, NOT to spend money on a measurement microphone.

Does anyone here charge clients to get a studio piano tuned for a session? I have always seen this as a normal thing studios (especially low cost studios) do and have had other clients pay for it without compaint but I have been trading emails with a prospective client recently and she seems fairly put off that I am asking her to chip in 1/3 of the tuning cost for her session.

I have heard that some people tune their pianos slightly different for recording...