The Musicville couch gag

The Musicville couch gag song is the sixth couch gag of Season 25 of The Simpsons. It is the longest couch gag of Season 25 so far. It's introduced with "A Silly Simpsony" (a parody of Disney's Silly Symphony film series). 
The Land of Springfield is a magical, musical land where the town and all of its citizens are musical instruments, who all happily play all kinds of music. Bart and Lisa tells about the magical, musical land where the town where are musical instruments. The Simpsons (with Homer as a tuba, Marge as a trombone, Bart as a trumpet, Lisa as a saxophone, and Maggie as a French horn) are driving home in their car (depicted as a grand piano). When they stop for a moment at a music note shaped traffic light, Lisa jumps out and sees a sign telling about a jazz festival. When she sees the fun that's going on in the distance, she gets excited and heads to it, but then Mr. Burns (as a bassoon) and Smithers (as an oboe) appear, and when Burns sees the sign for the jazz festival and then Lisa happily heading towards it, he gets cross and has Smithers put up a sign reading "Classical Music ONLY!"
Lisa is then seen happily walking (and playing herself) along up the street, passing Apu (as a sitar), Moe (as a cello) and Barney (as a tuba) along the way, but then Burns and Smithers appear behind her and they release his hounds (as xylophones) after Lisa. Lisa runs for her life and then turns into an alleyway, but is cornered and trapped by the hounds and Mr. Burns then captured. She and the rest of her family are taken to the Nuclear Plant (with it's two large chimneys depicted as two large organ pipes), where they are bound to the wall with chains and guarded by Eddie and Lou (as cellos). Mr. Burns had also brought everyone else in Springfield there as well, then he steps up onto a podium and conducts everyone to start playing, forcing them all to play classical music in a symphony.
Lisa, upset and angry at how Burns will not allow any other kind of music and how he is forcing everyone to unhappily play only classical, decides to take a stand and starts to play jazz music, which makes her chains release from her. Bart starts to play as well, which also breaks his bonds, and plays along with Liza. Then the rest of the Simpson family start to play and break themselves free as well, then everybody else in the symphony begins to happily play jazz along with them. Mr. Burns is extremely cross at how everyone is playing jazz instead of classical music, but everyone soon starts to gang up on him, then his Nuclear Plant explodes and Burns is sent flying towards Metalville, where Nelson Muntz, Dolph Starbeam, Kearney Zzyzwicz, and Jimbo Jones (all as electric guitars) gang up on him and start to play a brief rock version of the Simpsons Theme, much to Burns' dismay.
After Burns is defeated, Lisa puts a sign that reads "All Music Welcome" over the one Burns had put up, and she, her whole family, and everyone else in Springfield, head to the jazz festival where they happily play jazz techno, country hillbilly, rock (which Burns is now bound in chains himself and forced to listen to), and old folks' music, and then finally they end playing a jazz version of the Simpsons Theme.