COMPRESSION TRAINER

01What compression actually is

A compressor is an automatic volume knob. When the sound gets louder than a line you set, the compressor turns it down for you — fast, every time, more consistently than any hand could. That's the whole idea. It makes the loud parts quieter, which shrinks the gap between the loudest and softest moments. Then you turn the whole thing back up, and now the quiet stuff is louder too.

That's why a compressed vocal sits in a mix instead of jumping out and ducking under. It's not adding anything. It's evening out what's already there so you can hear all of it.

02The transfer curve and the meter

The graph maps input level (bottom) to output level (side). A straight 45-degree line means no compression. The bend is where the compressor starts working: below it the line stays at 45 degrees, above it the line tilts flatter so louder inputs get pushed toward the same output. The flatter that top section, the harder the compression. The bar on the right is the gain-reduction meter — it drops by however many dB the compressor is pulling back right then, and the exact number sits right on the handle. The strip under the graph plots that reduction over time, so pumping becomes something you can see, not just feel.

03Threshold and ratio

The threshold is the line. Drag the curve left to lower it so more of the signal gets caught; drag right and only the loudest peaks cross it. The ratio is how hard it pushes once over the line — 4:1 means 4 dB in over the threshold becomes 1 dB out. Scroll the graph to change it and watch the top tilt.

04Attack and release — where the punch lives

Attack is how fast it clamps down after the signal crosses the threshold; release is how fast it lets go. A slow attack lets the transient — the crack of the snare, the pluck of the bass — through before it grabs, which keeps things punchy. A fast attack catches the transient too and flattens it, which sounds dense, or dull if you overdo it. For release: too fast and you get audible pumping; too slow and one loud moment ducks everything after it. A release that breathes roughly in time with the track is the trick.

05Knee, makeup, and the honest A/B

The knee is how abruptly compression kicks in at the threshold — a hard knee snaps on, a soft knee eases in over a few dB and sounds more natural. Makeup gain adds the level back after the compressor pulls it down.

Here's the trap: louder almost always sounds better for a few seconds. That's why this tool has separate switches. BYPASS is a clean dry reference that never moves. AUTO-GAIN, when on, keeps the compressed signal at about the same loudness as the dry one so your A/B is judging dynamics, not volume.

06The four classic flavors

People name compressors by their circuit because each grabs the signal differently. This tool can't truly emulate the hardware — the browser's compressor is a clean digital one — so the flavors here are a teaching model: each changes the attack/release feel, the knee, and adds a little character so you get the personality, not a clone.

07Delta — hear what's removed

Hit Δ DELTA and you hear only the part the compressor is taking away. It's the difference between the dry and compressed signals. On drums you'll hear the transients and the loud hits getting grabbed; on a vocal you'll hear the loudest words. It's the fastest way to understand what a setting is actually doing — if delta is grabbing the body of every note, your threshold is too low.

08Parallel compression

One more move worth knowing. Keep the dry track and blend in a heavily compressed copy underneath. The dry part keeps its punch; the squashed copy fills in density. Loud and controlled without losing the life. Some call it "New York compression."

09How to actually use it