a muted, monotonal quality

Nine thousand of the 14,000 performers were PLA soldiers, who had endured some rehearsals that lasted 48 hours.
As day turned to twilight, the sky changing from light gray to gun-metal gray as the grimy air filled with humidity, 91,000 spectators began enduring six sweaty hours of pre-ceremony and ceremony.
For all its grandiosity, there was a muted, monotonal quality about much of the cultural exposition that reached a dramatic climax with 2,008 white-clad martial arts performers, bursts of fireworks and acrobats dangling from ropes at roof level.