D4 is a "Dynamics Processing Tool" that breaks up audio into "processing zones" so you can control different levels as needed. Each zone has separate attack, release, and gain settings. Unlike ordinary compressors it can be a compressor, expander, compander, leveler, de-esser, ducker, dynamic restorer, limiter and everything in between.

New to the D4 is the concept of zone gain control (ZGC). With ZGC on, audio outside the thresholds will retain the ratio set for that zone. With ZGC off, audio outside the zone remains unaffected.

D4's input meters and input gain are on the left of the plugin. From here the zone processing takes place in the center of the layout. Finally the output meters and output gain are on the right. All the attack, ratio, and release setting are below this. In addition to this layout, the extensive key section is now viewed in its own window by clicking a button above the i/o map. This allows the key section to be utilized when needed, or hidden when not in use.

Processing:

• Four (4) individual, completely user configurable compression "zones" w/ separate attack, release, and ratio per zone.
• Zone Gain Control.
• Input and output "cloud" meters.
• Auto-Limiter.
• Side-chain (depending on host support*).
• User selectable key (left, right, both, side-chain*).
• Peak or RMS compression analysis of key.
• Look-ahead.
• Three (3) key audition modes.
• Up to three key filters.
• Seven (7) key filter types available.
• Automatic gain compensation.
• Target and processed key meters.
• Input and output peak hold meters with over indicators.
• Input and output trim with +/- 36 dB boost/cut.
• Supports sampling rates up to 192 kHz.
• Works in mono or stereo.
• Multi-processor/Advanced multi-processor (AMP) capable.

Interface:

• Interactive graphic compression display.
• Ratio, attack and release sliders.
• Zone linking - links contiguous zones to maintain relationships.
• Attack and release lock to maintain same value for multiple zones.
• Interactive key filter graph.
• Keyboard text entry of parameter values.

General:

• Integrated SAVE and LOAD.
• Two workspaces.
• Copy settings between workspaces.
• Supports host-based parameter automation.
• Supports Pro Tools D-Control.