"You've got the touch... You've got the power... Yeah!"
— Stan Bush, "The Touch"
"You hear that? The theme song's playing! That's how dead you are!"
— Vegeta lampshading this trope during the GRAD boss battle in Renegade for Life: Metal Gear Rising Revengeance - 7 -
Even Uno notices that the music has given Fate a boost in magical power... Or that Fate's magical power boost started the music, I'm not too sure which. Both are equally valid options.
"Someone stop him before he starts singing!"