Piano Forum

1) That had never occurred to me - nice idea, though it's perhaps unlikely that Chopin would have had enough experience of trains to be aware of the Doppler effect from them.

2)  Calculations of the Doppler effect give the relative change in frequency, so for a change of a semitone (or any inyterval) it doesn't matter what note you start with. In equal temperament a semitone corresponds to a frequency of the 12th root of 2 (because there are 12 in an octave, which is a 1:2 ratio), about 1.0595. Using the formulas from the website above, and bearing in mind that you have to consider the train both approaching and receding (so the "true" note, which you would hear if the train was stationary, is somewhere in between), I think that to give a change of a semitone the train would have to be travelling at about 10 metres per second (36 km/hour, 22.4 miles/hour). The calculation depends on the speed of sound, which can vary according to air pressure, and also wind speed, but I don't think these would change the answer much in the normal range of conditions.

Thanks for the response!  Would be nice to get a second person to check this.  I clicked on your link and the web page is not available to me (plus I’m a little lazy).

Everything you say sounds correct to me and I will assume you are correct.  This takes away my theory of a train roaring by since 22 MPH is hardly roaring.  But I read just now that passenger trains of the 1830’s went about 30 MPH.  I spent about 5 seconds to see if Chopin ever rode on a train.  Nothing came up.  Trains in 1848 could go 60 MPH.  Chopin wrote Op. 53 in 1842.

Here is the sound of a train passing by my guess at about 30 MPH.  There is not a train whistle blowing (for example) as it passes.  So, it is maybe impossible to determine the amount the pitch changed due to the Doppler effect. But the Doppler effect is still clear in the train recording below.  

This train is not as fast or exciting as Kissin’s 16th notes in my sample recoding link above of the Op. 53.    I don’t normally like much of Kissin’s playing, but he nailed this one!

Train passing by (start at 12 second marker):