INSTRUCTIONS: Convince someone to sing into your phone for you. Call the SF0 Batphone from the phone number in your SF0 settings, and hand the phone to your victim friend. When they have finished, offer to return the favor for them, and if they take you up on it, sing to whomever they call.
Link the proof from your media page. (This should be an option when you submit your proof.)
bonus points for use of the word "flagon"!