fred: hey do you know anyone who can teach me how to play the trumpet
ron: why
fred: i wanna wander around the dungeons and annoy the slytherins
harry: technically you don’t actually need to know how to play it for that
fred: you have opened my eyes, harry
This is completely in character omg
Plot twist: after a few hours of Slytherin-annoying, Fred encounters a Slytherin who plays trumpet and they are like. SO offended, not at the noise but at the poor technique and they are all “Give me that and listen: HERE is how you hold it, THIS is how you blow it, here is this note, that note, another note, now try and make a reasonable sound.”
To make a long story short, Fred learns to play the trumpet.
So does George, because he snags the trumpet and pretends to be Fred one day and gets the same lesson. Trumpet!Slytherin can always tell them apart by their different skill levels: Fred gets exceedingly good at the trumpet, while George masters the basics but then thoughtfully asks Trumpet!Slytherin if they know anybody who plays the bassoon.
By the time they graduate, the Hogwarts Interhouse Nuisance Orchestra consists of three trumpets, one bassoon, four tubas, an electric guitar someone’s charmed to work in Hogwarts, eleven drums of varying sorts, and a set of bagpipes (Professor McGonagall).
No talent is required, only enthusiasm and friendliness.
Next year they’re down two trumpets and a tuba, but a newcomer from a muggle household introduces the concept of contrabass and hyperbass instruments, Harry Potter happily throws a large sum of his inherited money at providing odd instruments in amusing quantities, and such events as the Monthly Nuisance Parades and various holiday concerts are conducted with several instruments that have to be levitated along, including a harpsichord and a concert grand piano.
When Voldemort tries to invade Hogwarts, he’s struck with a near-literal hammer of cacophanous sound that drives him right back out the doors screeching in pain. The final battle goes a bit differently, and every year afterwards there’s a reenactment on that day in which a cartoonish effigy of Voldemort is escorted out of Hogwarts by the Hogwarts Interhouse Nuisance Orchestra, pelted with garbage, and set on fire.
By the time Harry’s kids get to Hogwarts, the musical concept has spread and there are several chamber ensembles, jazz bands, filk circles, a proper orchestra, a band that plays at quidditch matches, and several clubs based around specific instruments or musical styles.
