As it happens I do have a number of compressors in stock so was able to do some experiments today……
At first I tried putting some classical music through the limiter circuits of my new 828 Mk3 mixer. This was not a success, the limiters do the job of preventing overloads perfectly, but when pushed, add a degree of harshness without accenting the quiet sections sufficiently.
I also tried my P38EX mastering compressor, but I think this one is generally too well behaved; it refuses to carry out the necessary increase on quiet passages.
Lastly I tried a combination of two TFPRO538 stereo compressors in a 500 series rack. Having thought about it overnight I wanted to try using a fast and sharp compressor to bring up quiet sections and to follow it with a much slower’heavy’ compressor to operate more as an automatic gain control for the complete signal.
Of course, the 538 is a sophisticated compressor in its own right; it already has shaped attack and release curves and reacts at different speeds depending on the level and dynamics of the signal, running two of them in series I expected a greater degree of control.
The system works extremely well. I have the first compressor set with about 18dB of audio gain, slowish attack and fast release, with a compression ratio of about 10:1.The second compressor has about 15dB gain, fast attack and slowest possible release. The ratio is about 6:1.
The result is an extremely complex array of time constants that hold the maximum volume level stable and brings up the volume of quiet sections by as much as 22dB with remarkably little noticeable level shifting. The result is acceptable quality and I think, offers a solution to the particular problem.
I’m not sure that this is a practical answer as these compressors are not cheap, but it is certainly an answer. Ideally, I would design a completely new compressor fitted with dual sidechains and optical circuits to emulate the effect of the pair of 538s, but I think the cost would actually be greater than for a pair of existing 538 compressors!
If you are interested in taking this further, please email me at firstname.lastname@example.org