A belated answer to ced2's post. I have been rummaging in the attic for my sources, but too few of my old books have survived purges.

E.S. Cox, in "Locomotive Panorama", described holding a concert for train whistles, and stated that the A4 chime whistles sounded rather feeble on other engine types because of long pipes, full of condensation. Terry Essery, in "Steam Locomotives Compared", suggested that some auxiliaries normally worked from exhaust steam, but were automatically fed from live steam when the regulator was closed. Unfortunately he doesn't state whether the whistle was one of these. ced2 is probably right; it would seem unusual to use exhaust steam for the whistle, but I will have to re-read the voluminously detailed Essery again, more carefully.

I looked at some other steam train videos on YouTube. One I liked was of a Black 5 on the notoriously steep Settle and Carlisle line, pulling ten carriages and a very dead Type 47 diesel locomotive up a gradient. It produced smoke to rival Mount St. Helens, but it pulled.

My dream for new design or build, would be for a properly designed and draughted "Garrett". These never did well on British main lines; there was one whopper (the LNER U1) which banked heavy coal trains up the Worsborough Incline from Barnsley to Penistone, and thirty-three also used for heavy freight on the LMS. This class was badly designed in detail, with inadequate axle boxes and brakes.