The performance, usually the live performance is one of the most important moments in all music anime. If it’s good, it makes the characters feel more real and alive. If it skips the performance, it makes us wonder why it is a music anime in the first place.
Many music anime such as Stop This Sound, which I recently watched, have so much dialogue during the performance. As they play their instruments, the characters watching them play would make remarks like, “It’s very good. I feel like all the seasons have changed” or “oh my God they all play the impossible notes in sync even though it’s… well, impossible!!!” The remarks, to me, breaks the flow of the performance. I want to listen to the performance and let me catch it first hand how awesome or awful they play and how good they’ve become. But I can’t because other characters interrupt me and describe how they play to me.