THE siren of alarm, which heralds the passage of police car, fire engine or ambulance, is a symbol of political order, a re minder that no disaster is so private as to lie beyond the reach of public concern. On summer nights the sound fills the air above our cities, advancing from every quarter, resounding now near, now far, changing position with the suddenness of a mirage. When focussed at last, it is because you lie in its path; it becomes then single-minded and dangerous. It sweeps forward, murdering sleep, sending up sprays of anxiety, shouting of a catastrophe that might well be yours.

Should you be lying in bed in London, you hear a steady cacophonous alternation of sounds, each crowded with micro- tones, distanced by a minor third. It is a parody of the cuckoo, but also a reminder of the chorus's plea to Stravinsky's Oedipus: e pesta serva nos. The unbroken march of sound is a symbol of law and transgression, a renewed declaration of government and commonwealth in the face of foreseen aberrations.

The sleepless listener in New York hears something quite different. It begins as an unearthly wail, rises in pitch and volume to a point of anguish, sobs, chokes, and then bursts out in fiendish laughter. The wailing resumes, works to another climax, and then again turns to laughter. The sound has a spectral, frightened quality: not the voice of the law outraged, but that of the crime discovered. The American ...