Ace Frehley performed in South America last month and posted a video from his show in Buenos Aires with the caption, "You'll never hear 'Parasite' the same way again... This is how it's done."
He was referring to something that Rush also encountered in South America in 2002: audiences singing along to the instrumental sections of the songs. So, in the case of "Parasite," the audience accompanied the instrumental opening, just like they did with Rush and the all-instrumental "YYZ."