"Kirlia, the Emotion Pokémon. If its Trainer becomes happy, it overflows with energy, dancing joyously while spinning about." – Pokédex entry for Kirlia.
"Using Orpheus and Eurydice together in battle makes a lot of sense, doesn't it?" Kumiko noted. "Since they've got a better psychic connection with each other from being twins, they can coordinate their actions from two points of view without us telling them what to do, and warn the other of incoming attacks they can't see."
"I agree, especially during the final of the Double Battle tournament we participated in." Reina added. "It still seems crazy to me that both of them evolved into Kirlia at the same time there. Maybe their psychic bond goes deeper than we think."
"Yeah, but I still think it was you playing your trumpet when they were figuratively pressed against the wall which caused them to evolve." Kumiko thought back to their match with Nozomi and Mizore. "Wait. That made me notice a pattern. Didn't most of our Pokémon evolve when music was being played? Is that what triggered their evolutions?"
"Now that you mention it, it seems to be the case." Reina replied. "Though I've got completely no way to prove this, that's actually a plausible theory. But I wonder what could be the root cause of it…?"