presuming this is a nonunion arena?
can you talk to folks who've worked w the theater or those involved to get their feedback? Are these people who will advance your career or have connections that make it worth the challenge?
If the promissory note only expresses that you will be paid (and hopefully how much), you are entitled to know what their expectations are for that pay, so they can't turn around and say well, you didn't do x or y, so we aren't giving you the amount discussed. And no, it's not a contract, but nonunion work is often done without one. But you are entitled to ask them why they use this, in a very non-threatening, "just wanting info" kinda way (think of it as a pre-nup). Have they been burned before?
I think it's worth it - and fair - to say "I need to know what your expectations are, what you expect of me, so there is no confusion and I am not making any assumptions about my job" - you can even phrase it as knowing what they expect so you can make sure to fulfill their needs. Of course, this gives you the opportunity to see if their expectations are realistic or within the parameters you're willing to accept for yourself, and to write it out so you can point to it later (or, perhaps, email a "this is what we talked about, can you make sure I heard you correctly email" which will document the discussion in case there are issues later on.
And yes, sounds like a micro-management kinda situation, where you may be very, very unhappy. Have you already been to productiojn meetings and done other work yet? Is your time and skill being valued and respected?
good luck - and let us know what you decide