The Music Hall sent an email saying we need to arrive 1 hour before performance starts. Is this a new policy? If we arrive 40 or 30 minutes before the performance will we have plenty of time?

Yes, 30 mins is plenty of time. But it does depend on the performance and if you're getting refreshments, which might take some time.

It is best to arrive early due to parking and traffic they have strict rules to late seating and stick to them it keep the theater experience great so to be on the safe side arrive early

Yes you will.. i git there maybe 30 mins before