There's A Light
From RockyWiki
"There's A Light" is a lyric from the chorus of "Over At The Frankenstein Place". It is a part of Audience Participation where the audience uses handheld apparatus such as lighters (Flicking your Bic), flashlights, etc., to create lighting effects in the darkness of the theater when Brad Majors and Janet Weiss arrive at the castle of Dr. Frank N. Furter. Modern audiences primarily use cell phones to achieve this effect.