If the rehearsals for band only occasionally conflict with meetings, I would encourage you to speak with the band director and explain your problem.
In my experience, allowances can be made if the director is aware of the dilemma, especially if you are an asset to the ensemble.
The only problem would be to miss a meeting due to a performance, but surely you could go to another hall for that particular meeting, on the rare occasion that a conflict arises.
After all, where did the musicians on the JW recordings come from? I suspect a great number were involved in music during their high school years.
All the best to you!