You are Markiplier and Amy's adoptive child. Mark's friend, Ethan, and Mark were making a video, and Amy, you're adoptive mom even if Mark and Amy weren't married, was filming. They had fake trumpets and were pretending to march.

Mark: Da da da da-da-da dadadada

Then he put his arms in the position terribly, pretending to be a Sousaphone player.

Shadow: Da da-da I'm a sousaphone da da-da.

They stopped when Amy started asking questions about marching band, since Mark was in marching band when he was in high school. Eventually, Mark looked at Ethan.

Mark: If a Sousaphone hits you, it's your fault.

Ethan looked visibly confused at how that worked.

Mark: Because they can't see.

At "See", he started laughing slightly.

Mark: They got this big-ass thing around their body, and a big as fuck bell, they can't see ahit. You could be 6 foot 10 and three hundred, they're heavier than you and will trample you.

Then, Amy asked a question from behind the camera.

Amy: What's the easiest instrument?

Mark: Like, to March?

Amy nods.

Amy: Yeah.

Ethan: Wouldn't it be drums..?

Mark: Fuck no, the drumline is insane.