If your district isn't going to allow you to go to when the training is offered, and if they offer any training at all for other specfic subjects, then they absolutely need to provide you ACCESS (sorry if I was clear) to receive commiserate training in your subject area. The beauty of TMEA is that they provide comprehensive training.
And since most districts aren't providing any band-specific or even music-specific content, then you have every right to exepect to have the time to go.
They might not pay for it, they might not even provide the sub days for it, but they need to allow you to go and not restrict that.
Otherwise, how else do they expect you to get the required CPE for continued certfication?