On a Manehatten rooftop.
“Isn't it obvious? I'm going to train you to be this Earth's batma- re. In a few months you will be able to take on and prevail against any foe! You will be Equestria's greatest hero! Then there will be no way that you'll be called worst pony!”
“Now see here. If you think I'll- Where is that music coming...” She looked to her right. “from.”
Taking up the other half of the rooftop was an orchestra. Having recognized the yellow earth pony mare playing the violin, Applejack went up to her and hissed, “Fiddly is that you?”
Not stopping playing her violin she said, “Hey cuz. Bit early for Nightmare Night ain't it?”
“What are you doing here?”
“Darn if I know. Was minding my own business when poof here I am playing this sweet fancy musical number that I never heard of before.” There was a ripple around her as ponies stopped playing.
The cello player who could have been Fiddly's twin sister, except that she was gray, stood up.
“Ponies! We are professionals. When we play we do not stop until we reach the end. Neither bores nor drunks nor rain of screaming turkeys*”-she turned to face Applejack and growled out- “nor the chaos that just happens around a Bearer of the Elements of Harmony” she continued normally, “shall stop us from justly completing our performance.”
* Excerpted from the final findings on the Commission On Why We Have Not Heard of Changelings Before This: We believe that part of the musician motto is the earliest, if veiled, modern reference to a changeling invasion. First published in 634 CE. Dissenting opinion states that it is more likely to be a reference to a Thanksgiving holiday event where some pegasi, possibly drunk, did not know that turkeys can't fly.
A male voice spoke up, “But Octavia-”
“Don't but Octavia me, Riff. This is a performance, however weird it may be. We are professionals; we shall act like it.”
Fiddly waved her bow to get Octavia's attention. “Talented amateur here.”
“Which would explain your talking while performing.” Octavia sighed. “Can anypony here honestly tell me that they do not want to complete this piece? Anypony? Even talented amateurs? No?
“Then let's do this!”
Bat-Mite interrupted, “One question before you start!”
“What?”
“What makes you think that this masked mare is a Bearer of the Elements of Harmony?”
“Oh gee, let me think. Ponynapped from across the country. Magically compelled to play a piece of music that I- Anypony? No? Make that nopony here has heard of. And the only relatively normal pony here without a musical instrument in this living nightmare, is her. Whom else would she be?”
Applejack turned to Bat-Mite. “That does make a lick of sense.”
“OK, Ponies get ready!” The musicians took their places. Seeing that they were ready Octavia said, “Once more, from the top!”
They started to play.
Applejack and Bat-Mite moved over to the edge of the rooftop.
“What in tarnation did you do?” Applejack hissed quietly.
“I thought that some mood music would set you in the right mood.”
“And you thought ponynapping several dozen ponies to do so a good idea?”
“Music from a full Orchestra just has more gravitas than music from a FloatImp.” He pulled out a small rectangular device from his belt.
Applejack facehooved.
“What? Unless I keep them here longer, once they finish the song they will return to where they came from. And for their time, they learn the awesomest Batman Theme song ever! What's the bad?
Applejack groaned.