This type of old recordings have sometimes a dynamic range lower than reality. And wisely manipulated to be reproduced in domestic systems.
Please read about the great Decca's we all enjoy greatly:
from
The Decca Sound: Secrets Of The Engineers
Compressors Off
The sound of rock and pop music is very much shaped by various kinds of compression and distortion. Classical recordings, on the other hand, tend to have a greater dynamic range and aim to capture the instruments as they are by affecting them as little as possible. It is still necessary to process the sound to a certain degree so that it can be reproduced on domestic playback systems, but automatic levelling tools such as compressors, which fundamentally alter the sound in a variety of ways, have not generally been used at the recording stage.
“Compression was something used in the pop world to get maximum dB on the tape for AM radio,” says Mike. “Decca didn’t use compression for classical recording but there was
gain riding. The idea was that a loud movement would peak at zero, but the soft movements also had to come close to match. We’re not talking about ferocious gain riding, just little tweaks.
“The overall gain was basically set,
but the other parts were adjusted depending on what the producer wanted. There’s an instance in the last movement of the Szell/Curzon Brahms Piano Concerto No.1 where you can hear the gain being pulled up because it was too low. But it was done very subtly and a good operator would never reveal in the sound that you got off the record that he had been doing that. But they had to do it.
“When Kenneth Wilkinson worked with conductor Charles Gerhardt for Reader’s Digest, Gerhardt was saying ‘Coming up, we’ll need a little more of this, coming up, a little less of that,’ and Wilkinson would have been
moving the potentiometers a little bit here and there.
So the producer was listening to the music and anticipating what was going to happen.
End of quote.