Most districts are ALWAYS short on subs.
With the pandemic, many people who WOULD work as subs (retired teachers, for one) aren't going to do so because it's not exactly safe.
So an job/role that already has issues with staffing is now having larger issues with fewer available workers.
So yes, we're all being asked to cover extra classes. I've had Orchestra kids in my band hall every week all year long. We've got a communications teacher who retired over Christmas, and none of his classes have had a sub since then. Those kids have to go *somewhere* even if there aren't many of them on campus.
No, you're not going to get paid extra - this is part of "extra duties as assigned." Your district isn't being cheap, you're just not looking at it from the perspective of "there's more to running a school than letting the band director just teach band."