Season 1, Episode 10.
"Pinkie Pie, you are so random." Twilight Sparkle criticized.
"And you are all so stubborn!" Pinkie Pie screamed in return. Not a single friend of hers believed she had any real contribution to what was going on. They were so wrapped up in their own solutions that they didn't or couldn't pay attention to the solution being formed right beneath their noses.
In spite of Fluttershy's knowledge of nature and critters she was absolutely clueless on what a parasprite was. As a result it was assumed nobody knew how to fix their pest problem, but Pinkie sure knew! None of her friends, or any pony she knew of had to deal with a crop of well cultivated rocks being devoured in a single week, but that was a memory Pinky Pie could not let go and she was determined not to let it happen again.
Pinkie was distressed. She had moments where she held out hope, but she was ignored at every turn. Every pony seemed to have things handled as best they could. "Pinkie is just being Pinkie" as some have put it. A terrible insult to a beautifully glowing personality. And unfortunately something that may come back to bite her and her friends later on..
She stashed her arsenal in the bushes at the southeast end of town so that the parasprites wouldn't find them easily. (the flute was a nasty casualty of this war) As soon as she got the necessary items together, she went to work fixing the problem and saved the day! Good thing she found that trombone first, it was the most important instrument after all.
She was alone in her fight! Pinkie Pie, the unsung hero with all of the music.