movie automatic volume control audio compressor

Sometimes you need to automatically adjust audio-volume or gain, for several purposes. The first time in my case to perfect the modulation depth of a (HAM) amateur transmitter, but later for more than that. To keep the neighbors’ happy, I cannot watch movies late in the evening. And do not forget music…!
Most of the movies i see on tv or computers, contains audio mixes mend for large auditoriums and theaters. There is an enormous difference between the dialogues, the music and effect sounds. To help average the differences, automatic gain adjustment comes in handy. In the past i build a unit with transistor or fet as active attenuator. Not all that good, little distortion but did the job.
Until I read an article about the strange behavior of diodes, when used below their threshold. You can alter the resistance by applying a small current. I experimented out of curiosity. But before I know it, build a complete stereo gain control with compressor and limiter. From parts out of the old stock or junk box.