As the Airbus 320 taxid gently to the runway yesterday at Philadelphia (flying GlasgoW-Philadelphia-San Francisco-Redding), sitting in an aisle seat over the wings, I could hear the beat rate between the engines slow down and speed up as their respective revs changed slightly. For a few seconds, they would slow to almost unison. Those who sing will know the phenomenon where, listening to a singer, one feeels one's throat and body tense in sympathy. On that plane, my left arm (i tune left-handed) was itching to move something with a tuning lever, to achieve unison!
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