The City as Music
The city is a living organism to which we choose to belong. It exists because coming together unleashes great economic, intellectual, social surplus, the whole is far greater than the sum of parts. We are intelligent, listening parts of the city, and the sound of the city includes the sound of us.
The variety of sound: One can sort the sounds of the city in many ways: by originator, by instrument, by loudness, by size (or wavelength) by their cyclic, constant or unpredictable nature, by where you are most likely to encounter them, but it is these, the actual sounds of the city itself that we mould and shape when we create a room or a street, town square, or garden.
Water. A city is always being washed by water, in its various forms: rain, sleet, hail, snow, streams, rivers, through fountains, baths, taps, sprinklers, gutters, gargoyles, spouts, hoppers, pipes, chains, channels and drains
Air: the rustling of leaves, the gusting of wind and its effects, whining and moaning of windows, rattling of shutters,
Thunder: occasional and deafeningly loud
The sound of bells.
Transport: aeroplanes, trains, buses, lorries, cars, motorbikes, milk floats, bicycles, together with their attendant horns, sirens and bells
People going about their work: digging, constructing, drilling, hammering, working machinery, revving engines, sawing, painting, writing,
People playing: the creak of swings and roundabouts at the playground, the bounce of a wall and the thud of leather on willow, making music
Canned music, the radio, TV, cinema
The sound of the human body itself: people singing, talking, whispering, breathing, farting, walking, running, jumping, the sound of the heartbeat
Machinery by itself: the sound of fans, pumps engines and transformers, mains hum.
Other animals: dogs, chickens, birds, foxes rats, flies, wasps, beetles, birdsong.
The loudest sound man ever heard until gunpowder was thunder
The loudest man made sound was bells: whole districts laid out to the distribution of bells which can carry about a mile and a half: washing the space periodically with a purifying sound. Bells are used to mark the passage of time, to inform, to claim the territory.
The sound of the city as a whole. Each city, each community has its characteristic sound: its soundscape. Cairo, with the layered sounds of car horns, dogs barking... New York with a song of sirens... cities of bells, cities of water.
Consider taking a trip in a balloon on a clear temperate day. As you rise above the city, with its doors and windows open, people working in the streets and gardens, birds in the trees, dogs barking, the trob of traffic in the background, as the sound of all these different and individual activities blend into a richly woven carpet of sound, one can sense the underlying connectedness and unity of the city through its sound.
Yes the sound of the city has changed over the last few hundred years, the overall noise has increased:
Here is Luigi Russolo in 1913 (note the date) , glorifying the throb of engines and the power of machinery
'Let us wander through a great modern city with our ears more alert than our eyes, and enjoy distinguishing between the sounds of water, air, or gas in metal pipes, the purring of motors (which breathe and pulsate with indisputable animalism), the throbbing of valves, the pounding of pistons, the screeching of gears, the clatter of street cars on their rails, the cracking of whips, the flapping of awnings and flags. We shall enjoy fabricating the mental orchestrations of the banging of store shutters, the slamming of doors, the hustle and bustle of crowds, the din of railroad stations, foundries, spinning mills, printing presses, electric power stations, and underground railways." 
And here is John Cage, posing a much gentler question in the 1960s
Which is more musical: a milk float going past a music school or a milk float going past a factory?
The city in detail - Soundscape can be considered at a global, corporate or intimate level, and all these scales coexist at any one time.
At an intimate level: one consider the sound in the space itself, the sound within the posts of a four poster bed, in a niche, a precise location
At a corporate level: the sound of a street or square
At a global level: the throb of the city nestled into its surrounding countryside.
What is the sound of the city waking up? The sound of a million people reaching for the going to work?
The sound of the city at work
the sound of the city in the evening
the sound of the city at night?
 Luigi Russolo 'The Art of Noises' 1913