Note to the reader: The percussionists may require special handing. A healthy supply of beer and the complete works of Neil Peart will keep them manageable.
After you have caused the marching band to yield, the players can then take the field.
If this is a recurring problem it's time to think about the acoustics of your space. Persistent infestations of musicians are often traceable too much (or too little!) reverb. Large open spaces attract the bands, insulated surfaces attract indie rock groups, often looking to found their first album. Kill one member and they will be replaced, and commemorative albums will be released. If you see completion albums? Just give up.
@futurebird @JuliusGoat You could also consider the economics of the area. While there are musicians who are immune, driving up property values can help deter the band from fully forming.
If nothing else works, consider a major construction project. They hate the noise. You will, too, but it might be preferable to a marching band.
And remember, we're rooting for you. We're all in this together.
This sounds like the bee lady on TikTok who's always saving the bees by finding the queen and moving her to a new hive.
"It's another great day of saving the woodwinds."