Russian theaters do not announce their playbill very far in advance. That is why the best time for planning evening events is 2-3 weeks before your visit, not earlier.
Very few Russian theaters - like Mariinsky or folk-show "Feel yourself Russian" - bother to advertise themselves on the Internet. In reality the choice of events is often more rich and interesting - but information about small concerts held at ex-aristocratic palaces, parks or churches is usually beyond the reach of tourists.
I can prepare for you a kind of report - what would be the best options for the dates you are interested in. When you decide what you prefer, I will buy the tickets (unless they can be bought only before the performance starts).
Please note: It is impossible to return the tickets. That is why 100% prepayment is a condition of this service.