Be very careful you are not wearing a "costume". As in Ogden, symphonies in Vancouver are attended by folk wearing all manner of daily attire. I wear a jacket and tie (never a PC): sometimes a business-weight black Argyle or a kilt-altered black or blue blazer and tie. Always a tie with a jacket.

At matinees I wear a dark tweed jacket.

If the majority of attendees in Ogden wear pretty casual clothing, I suggest you dress similarly: a shirt (and tie?) topped by a light, stylish "sweater" matching a base or over-stripe in your kilt. Definitely wear a leather sporran to match your belt (if you choose to wear one) and your shoes.

For shoes, wear black brogues (not ghillies) or polished slip-ons.

Smashing! but blending in, too.