You meant formality.
If the concert takes place during the day, here are some examples of suits I would recommend:


Or if it is in the evening:

I do not say that there are the most fashionable examples, but with today's fashion, looking sharp and classical has nothing to do with looking fashionable.

I always notice the dress of performers and I often complain on inappropriate or incorrect attire after concerts!

By the way, if we are talking about dress, let's see our favourites Ravel and Gershwin (and some other friends of theirs) in dinner suits:

Best regards, Dr