Low End Candy · Mac & Windows · AU · VST3 · Free
GLASSBOX
Learn compression in real time.
Compression is a black box to most producers — you turn knobs, something changes, and you can't tell whether it changed for the reason you think. Glassbox is the box you can see into: every number and shape on screen is measured from your own material while it plays, not asserted from a lookup table.
Tap elements for infoHover over elements for info
The actual plugin: SPLIT view, transfer curve, measured numbers, and the COACH — interactive above.
A real compressor first
Feed-forward, log-domain, using the gain computer and smooth decoupled peak detector from Giannoulis, Massberg & Reiss (JAES 60(6), 2012) — picked deliberately because it's the topology whose behaviour actually matches the textbook description of attack, release, ratio and knee. An emulation's idiosyncratic ballistics would make the plugin's own teaching false. And the transfer curve on screen is drawn by calling the same function the audio path uses, so the picture can't drift from the sound.
Threshold
to −60 dB
Ratio
to 60:1
Attack
0.05–250 ms
Release
5–2500 ms + AUTO
Knee
quadratic soft
Lookahead
true, running-max
Mix
delay-compensated parallel
Detector
peak / RMS
Sidechain
HPF + LPF + external + listen
Stereo
link 0–100%, M/S
Auto gain
K-weighted, LUFS/RMS
Four things a normal compressor doesn't do
See before and after
Default view is SPLIT — before left, after right, same window and scale. Rust is painted where the compressor took level away, teal where it gave it back. The threshold sits on the waveform at its true amplitude, and the detector level draws in white — the single best explanation for why a compressor sometimes seems to do nothing.
Measures what it claims
Short-term LUFS, peak, crest, gain reduction at three timescales, and a WORKING % — the answer to “is this thing even on?” AUTO GAIN is on by default: bypass becomes a level-matched comparison by construction, because a level difference contaminates your preference rather than merely colouring it.
Explains out loud
A live COACH says the most useful true thing available — nothing's crossing threshold, release is longer than a beat at this tempo, you're comparing 3 dB louder. Hover any control for ABOUT THIS CONTROL, plus a gold spotlight on exactly the on-screen thing that control provably affects. Standalone MYTHS each come with an experiment you can run right there.
What's Changing
A single transient captured at full sample resolution with 30 ms of pre-trigger — because attack is the control people get wrong most, and it's invisible at any sane zoom. Touch a control and the before/after diff lights up and labels itself. ATTACK and RELEASE each light only their own measured slice of the hit.
17 source recipes that watch your audio
Kick to master bus — each recipe carries why those times suit that envelope, the classic mistake on that source, and a gain-reduction target. Then DIAL IT IN watches your audio and moves the threshold until it actually hits that target, because no preset can know a correct threshold. Plus nine deliberately wrong demo presets, pinned by a test so nobody "fixes" them.
Stop guessing what the knobs did.
Free. Name and email, and the installer is yours.