1. Band and choir may not perform (sing, play) any "wind instruments" indoors at all. In short, if it requires air, we can't play it. Drums and orchestra are fine if distanced.
2. All students must be fully masked at all times.
3. When playing a wind instrument or singing, the mask is moved to the chin while the instrument is being played, and is replaced immediately after playing. Yes, even during measures of rest. And yes, ONLY outside.
4. All band members and choir students must remain at least 6' from each other at all times when playing/singing, even if outdoors.
5. Every 30 minutes, the ensemble must take a 5 minute break and clear the area completely to allow aerosols to disperse.
6. No more than 60 minutes of playing/singing may occur in any class period/practice, regardless of scheduled length.
These "interpretations" you talk about are what happens when no one is willing to step up and make policy - but then, when someone mandates "you must do this, and this, and this" and then kids get sick ANYWAY and they blame it on the band, the parents will sue the school.
It's all about avoiding liability.