We must suffer them all again.
Into this neutral air
Where blind skyscrapers use
Their full height to proclaim
The strength of Collective Man,
Each language pours its vain
Competitive excuse:
But who can live for long
In an euphoric dream;
Out of the mirror they stare,
Imperialism's face
And the international wrong.
Faces along the bar
Cling to their average day:
The lights must never go out,
The music must always play,
An example of synecdoche; the faces represent the people, the humans with their desires and insecurities. 
 Auden may be implying that these people in the bar have limitations; they may present an outward face but perhaps shallow inner lives.
September 1 1939