It's absolutely correct that pianos
made before the Second World War
had a much more mellow sound than
new instruments do. The trend
probably started a little later than the
1930s, but it peaked in the 1970s
when some Hamburgs were coming
out sounding like shattered glass.
Almost forty years ago, I owned a Chickering 33b 8'4" grand with Brown action and straight-strung plate from the early 1870's, and also have owned uprights from 1912 and 1914, as well as a Chickering Bros. Acoustigrand from 1905. There already was a shift in tonal style from the 1870's to the early 20th century.
The straight-strung piano had less power in the bass, but a remarkably evenly voiced scale, and a very sonorous, non-percussive tone. The Acoustigrand of 1905 was a 6 foot grand, but had more power than the 8'4" straight-strung instrument.
I sometimes wish I still had that Chickering 33b, but I don't have a place for it anyway. The tone was still good-- I imagine it had been rebuilt at least once. But the action parts were brittle and non-standard. This meant that a rebuild would have been highly customized and prohibitively expensive. I sold it to an antique piano restorer.
