Compressors, which can work in stereo-linking mode, preserve the stereo sound of the processed signal. This function becomes especially important during mixing, when a very heavy compression of a stereo signal is needed. If a signal is compressed at the extreme ratio, the stereo sound and even the whole mix can be significantly modified, because the signal level in the right and left channel can be rather different. And that can cause drastic changes of perceived stereo image of separated instrument and entire song sound. Stereo-linking balances out this difference after compression, but, unfortunately, not every music mixing and mastering studio has a compressor with such a function.
Nowadays, program emulations of the analog hardware devices are widely used, and all of them have different characteristics. It’s hard to imagine a modern sound studio without such software. Compressor plugins are among the most common tools, as they imitate the devices based on the optoelectronic elements (Opto). Similar to the auto mode (described above), an optical compressor has floating attack and release times, which have bigger values. When the compression ratio increases, the release time decreases, and vice versa. This helps to prevent signal distortions caused by over-compression. Optical compressors work smoothly and have a distinctive sound “warmth”, which is the reason of their popularity at most of professional engineers.