Possible Clues:

• 'Silence!'
• 'Shut your mouth!'
• One's mum making this drama with different recordings
• "Silence!"
• Having no cassette recording, there's absence of noise
• Total silence from evil doctor on two kinds of record
• No reaction from the gagged and blindfolded person?
• Mum making this? Don't look!
• No cassette and vinyl recording, no sound at all
• Nothing to listen to on playing back band's record