I was on someones  holiday email list a few years ago,  and received this soundfile.  It's a recording  of carols played on the whistle that would have announced changes in shift at one of the steel mills around here.  

The file came without attribution, so I called up the Doctor and together we figured out that it was a Smithsonian Folkways album, Calls and Whistles , field recordings by Tony Schwartz. This selection is under the track called  "Improvisation of Instruments").     I don't know  anything about the recording  circumstances , whether it was a staged event, whether Schwartz   happened to be in the right place.  There is a spoken introduction where Schwartz refers to an imaginative factory operator, but beyond that ...

I assume that at some point during the year, the engineer has to practice.  Does  he practice off-hours, maybe during the night shift?  Does the community around the factory grow accustomed to the sound of  mistakes, missed notes?  The same frustration that a church organist feels, practising in an open building.  I imagine the technique involved is  similar to making a tune with a bicycle pump, or with the same skill required to play a Theremin.  

Is  this something handed down, from senior to apprentice?  Is  it the bailiwick of one visionary, someone who will eventually retire?  Does  each factory have their performer?  Could  there ever be combined performances, a Pittsburgh Symphony of Sirens?

All the machinery, all the noise, the grime and pollution  - all gone now.  What's left is this recording. That factory whistle is a carrier wave, modulated by the landscape, captured in stasis by early  recording technology.  Now an artefact, laden with human activity.  

The picture is Steel Works in Winter, by Roy Hilton.

http://explorepahistory.com/displayimage.php?imgId=1-2-A1B