gave them a focal point: the voice of the leader reverberating through the plaza or stadium or park. Before tube amplifiers, the limits of our vocal chords made it difficult to speak to more than a thousand people at a time. (The elaborate vocal stylings of opera singing were in many ways designed to coax maximum projection out of the biological limitations of the voice.) But a microphone attached to multiple speakers extended the range of earshot by several orders of magnitude. No one recognized—and exploited—this new power more quickly than Adolf Hitler, whose Nuremberg rallies addressed
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