IDX Intelligent Dynamics.

IDX is a frequency-dependent compressor that works out for itself where a track needs controlling, driven by one main knob. Rather than applying gain reduction evenly, it acts on the frequency ranges holding a part back, which is why it tends to bring an element forward and add definition instead of simply making it quieter and steadier. It suits dull or unfocused tracks in particular, and works well as a foundation early in a mix.