What Is Compression? — The Core Concepts
A compressor automatically turns down a signal when it gets too loud — then you turn it back up. The result is a tighter, more controlled, more consistent sound. Pro-C3 gives you eight different "flavours" of how that happens.
The golden rule: EQ always comes before compression in your signal chain. Set your EQ Eight (or Pro-Q4) first — cut the mud, boost the presence. Then compress. If you compress first, the compressor reacts to the frequencies you were about to remove. You waste gain reduction on energy you didn't want anyway.
Gain Reduction (GR)
How many dB the compressor is pulling down at the loudest moment. A GR of -6 dB means the loudest peak is being turned down by 6 dB. Watch the GR meter in Pro-C3 — it moves in real time.
Target: -2 to -10 dB depending on elementMakeup Gain
After compression pulls the level down, Makeup Gain pushes it back up to match the original perceived loudness. Without it, compressed sounds just seem quieter, not better. In Pro-C3, enable Auto Gain for automatic compensation.
Always set after dialling ratio + thresholdThreshold
The level at which the compressor starts working. Everything above the threshold gets compressed. Lower the threshold = compressor activates more often and catches more of the signal. Start at -20 dBFS and adjust while watching the GR meter.
Lower = more compressionRatio
How aggressively the peaks are turned down once the threshold is crossed. 2:1 = gentle, musical. 4:1 = moderate, the most common. 8:1+ = heavy, used on vocals and ad-libs. ∞:1 = limiter (hard ceiling).
2:1 gentle → 8:1+ heavyAttack
How quickly the compressor grabs the signal after it crosses the threshold. Slow attack lets the initial transient (the "snap" or "crack") pass through untouched before compressing. Fast attack grabs immediately — useful for very consistent sounds.
Slow = preserves punch · Fast = clamps peaksRelease
How quickly the compressor lets go after the signal drops back below the threshold. Too fast = pumping/breathing artefacts. Too slow = compressor never fully lets go between notes. Auto release in Pro-C3 is intelligent and usually excellent.
Auto release is a safe starting pointGain Reduction Targets — How Hard Should You Compress Each Element?
Pro-C3 Compression Modes — Which One & When
Pro-C3's eight modes each model a different classic hardware compressor personality. The mode changes how the compressor "feels" and responds — same settings, very different results. Choosing the right mode is as important as setting the ratio.
Clean, precise, programme-dependent
The most transparent and accurate mode. Behaves mathematically — exactly what you set is what you get. No character colouration.
Smooth, modern, gentle compression
Similar to Classic but with softer knee behaviour. Very gentle and musical. Excellent for sources that should feel compressed but not obviously so.
Designed specifically for the human voice
Attack and release adapt automatically to vocal phrases and breaths. Manages dynamic swings while keeping the performance natural. One of the most useful modes in Pro-C3.
Invisible compression at the master bus
Zero colouration. The most transparent mode available — designed for master bus work where the goal is control without any sonic footprint.
Cohesion and glue across group buses
Adds subtle harmonic density while compressing. Makes individual elements feel like they belong to the same group. The "magic glue" sound of classic SSL mix buses.
Sidechaining, pumping, ducking effects
Designed for rhythmic pumping effects. When sidechained to the kick, it makes the entire mix duck rhythmically to the beat — a defining technique in electronic music.
Optical-style: smooth, slow, programme-dependent
Models optical attenuator compressors (like the LA-2A). The release is slow and natural — release time is automatic and programme-dependent. Very musical on bass and vocals.
FET-style: fast, punchy, adds harmonic colour
Models vintage FET compressors (like the 1176). Fast attack and release. Adds harmonic colour and "snap" to the transient. The most characterful mode — you hear it working.
Mode Quick-Pick Guide
| Situation | Recommended Mode | Why |
|---|---|---|
| Kick / Snare | Vintage | FET snap adds character and punch. Fast attack options let the transient breathe. |
| Electric Bass / 808 | Opto | Smooth, musical response. Preserves the note and pick attack. Sounds natural on low frequencies. |
| Lead Vocal (any genre) | Vocal | Programme-dependent attack/release adapts to the phrasing automatically. Designed for this job. |
| Pads / Strings | Clean | Smooth knee, no colouration. Gentle touch that doesn't interrupt the swell or release of sustained sounds. |
| Drums Bus | Bus | Cohesion glue. Elements breathe together as one kit. Adds subtle density. |
| Vocal Bus | Bus | Makes lead, BVs, and ad-libs sit as one unified vocal group without squashing any individual element. |
| Master Bus | Mastering | Invisible compression. No sonic footprint — just control. |
| Sidechain / Pumping | Pump | Built specifically for rhythmic ducking and sidechain effects. |
| Overhead / Room mics | Bus or Clean | Gentle glue. Ties the air of cymbals and room together without obvious compression artefacts. |
| Trumpet / Lead Brass | Vocal or Vintage | Vocal mode handles dynamic phrasing well. Vintage adds character on aggressive brass lines. |
| Flute / Wind (lead) | Opto | Smooth optical response preserves the breathy character of wind instruments without over-clamping. |
Every Parameter Explained — What Each Knob Does
Pro-C3 is more complex than a basic compressor. Here is every control — what it does, what to listen for, and safe starting ranges for beginners.
The level (in dBFS) above which compression begins. Lower = compressor activates on more of the signal. Watch the GR meter — if it's not moving, lower the threshold.
How aggressively peaks above the threshold are turned down. 2:1 = for every 2 dB above threshold, only 1 dB passes. 4:1 is the most common all-purpose ratio.
Time (in ms) before the compressor grabs after the threshold is crossed. Slow attack = transient passes through first (punchy). Fast attack = clamps immediately (consistent).
Time (in ms) before the compressor lets go after the signal drops below threshold. Too fast = pumping. Too slow = compressor never resets. Auto is excellent in Pro-C3.
How abruptly the compression kicks in at the threshold. Hard knee = instant grab. Soft knee = gradual, more transparent. Soft knee sounds less obvious and is better for buses.
Adds volume back after compression has pulled the level down. The goal: compressed and uncompressed sounds should feel equally loud (use A/B bypass to check). Enable Auto Gain for automatic compensation.
Blends the compressed signal with the uncompressed dry signal. 100% = fully compressed. 50% = parallel compression. Keeps the natural dynamics while adding density underneath.
Delays the audio slightly so the compressor can "see" peaks before they arrive. Allows faster, more accurate attack without clicks or distortion. Use 1–3 ms on transient-heavy sources.
Keeps the compressor engaged for a set time after the signal drops below threshold. Prevents the compressor from "breathing" on rhythmic material. Most useful on drums and bass.
On stereo tracks, Link = both channels compress together (avoids stereo image shifting). Mid/Side = compress the centre and sides independently. Link is the safe default for most sources.
Filters what the compressor "listens to" before making decisions. High-pass the sidechain signal so low-frequency energy doesn't trigger compression unnecessarily on the vocal or mix bus.
Increases internal processing resolution for cleaner transient handling, especially at high GR settings. Increases CPU use. Enable on individual tracks needing precision; disable on buses for efficiency.
Attack & Release interaction: These two work together. Fast attack + fast release = pumping. Slow attack + slow release = smooth but may not catch peaks quickly enough. For most sources: start with the attack time that preserves the transient you want, then set release to Auto and let Pro-C3 decide. Adjust manually only if you hear pumping or breathing artefacts.
Step-by-Step Workflow — How to Set Up Pro-C3 Every Time
Follow this order every single time you open Pro-C3 on a new track. Doing it out of order leads to inconsistent results and missed compression.
The Compression Workflow — In Order
EQ first — always
Open your EQ Eight or Pro-Q4. Make all your cuts (mud, mud zone, HP filter) and boosts (presence, air) before touching the compressor. The compressor will now only react to the frequency-balanced signal you want.
Choose the correct mode
Select the Pro-C3 mode for your source (see the Modes section). Vintage for drums/kick. Opto for bass. Vocal for lead vocals. Bus for group buses. The mode defines the character before you touch any other control.
Set ratio first, threshold second
Set your target ratio for the source (e.g. 4:1 for kick). Then slowly lower the threshold while watching the GR meter until it hits your target GR range (e.g. -4 to -6 dB for kick). Don't set threshold then ratio — you'll overshoot.
Set attack to preserve the transient you want
Ask: do I want this sound to "hit" first, then get compressed? Then use a slow attack (20–30 ms for kick). Do I want it controlled immediately? Then use a fast attack (5–10 ms for vocal). Listen to the transient, not the level.
Set release — start with Auto
Leave release on Auto. Pro-C3's Auto release is musically intelligent and avoids pumping in most cases. Only switch to manual if you hear the compressor "breathing" between notes or the sustain sounds unnatural.
Apply Makeup Gain
Enable Auto Gain or manually add gain until the compressed signal sounds the same loudness as the uncompressed signal when you toggle bypass. This is critical — without makeup gain, compression just sounds like "quieter," not "better."
A/B bypass check in context
Toggle Pro-C3's bypass in the full mix (not soloed). The compressed version should sound more controlled and consistent — not obviously "pumping" or "squashed." If it sounds worse, reduce the ratio or raise the threshold.
Consider the Mix knob (parallel compression)
If the compression sounds great but is killing some of the natural dynamics or life of the performance, pull the Mix knob back to 50–70%. This is parallel compression — you get the density and punch of heavy compression while keeping the original dynamics underneath.
The bypass A/B test is mandatory. Your ears adapt to compression quickly. After setting it up, bypass Pro-C3 and listen. If both sound equally loud (you set makeup gain correctly) and the compressed version feels more controlled without sounding "squashed," you've done it right. If the bypass sounds more alive, you are over-compressing.
Drums — Kick, Snare, Clap, Hats, Overheads
Drums are all about transients. The goal of compression on individual drum elements is to control the sustain and consistency while leaving the initial "hit" intact. The attack time is the most critical setting.
Key principle for drums: Use a slow attack to let the transient punch through first, then the compressor grabs the tail. Too fast an attack on a kick or snare squashes the snap that makes it feel physical and impactful. If your kick sounds "small" after compression, your attack is too fast.
Kick Drum
DRUMS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Vintage | 4:1 | 20–30 ms | Auto / 50 ms | 4–6 dB | Slow attack is the entire point. It lets the "thwack" of the beater hit pass through completely before the compressor grabs the sustain and body. Vintage mode adds FET-style snap and harmonic character. If the kick sounds thin, raise the release time. |
Practical example: Set attack to 25 ms. Play the kick. The initial punch should feel unaffected — the compression only catches the "boom" after the attack. If it sounds like the punch is being swallowed, increase the attack time to 35–40 ms.
Snare / Rim
DRUMS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Vintage | 3:1 – 4:1 | 8–15 ms | 60–100 ms | 4–6 dB | Snare needs a faster response than kick because the crack is much shorter. Compression adds consistency — it catches the louder hits and raises the quieter ones. Vintage mode adds the "snap" that makes snares feel present and alive. |
Clap
DRUMS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Classic | 4:1 | 5–10 ms | 60–80 ms | 3–5 dB | Claps are extremely transient-heavy. Compression tames the loudest hits without killing the crack. Classic mode keeps it clean and transparent. Fast release ensures the compressor resets before the next hit. |
Hi-Hat (Closed / Open)
DRUMS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Classic | 2:1 – 3:1 | Fastest available | 40–60 ms | 2–3 dB | Gentle compression only. Too much kills the natural shimmer and openness. The goal is light consistency — not taming. Often hats need no compression at all if they were recorded or sampled at consistent levels. |
Overhead / Room Mics
DRUMS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Bus | 2:1 | 30 ms | Auto | 2–3 dB | Gentle glue. Ties cymbals and room ambience together without killing dynamics. Bus mode adds subtle cohesion. When the kick hits, all the overhead elements duck slightly together — they breathe as a unit. |
Bass — 808, Electric Bass, Synth Bass
The goal of bass compression is evenness. Notes played softly and notes played hard should have similar perceived volumes. Bass is also where a limiter on the bus matters — a rogue bass peak can clip the master before you notice it.
808 / Sub Bass
BASS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Multiband / Opto | 3:1 (low band) | Auto (optical-like) | Auto | Even sustain | On 808s, the goal is consistent sustain across every note — not peak control. Low notes on an 808 are naturally louder than high notes. Opto mode (or Multiband Dynamics with only the low band active, below 200 Hz) smooths this out musically. Behaves like an optical compressor — slow and programme-dependent. Do not over-compress 808 or you lose the sub weight entirely. |
Electric Bass
BASS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Opto | 3:1 – 4:1 | 40–60 ms | 120–180 ms | 4–6 dB | Opto mode on bass is the most musical choice. The slow, programme-dependent response of optical compression preserves the pick/finger attack while levelling out the body of each note. Longer release prevents the compressor from "breathing" between bass notes. |
Synth Bass
BASS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Classic | 4:1 | 10–20 ms | 100–150 ms | 4–6 dB | Synth bass is often more consistent than electric bass, so you might need less compression. Use Classic mode for transparent control. The faster attack (vs. electric bass) works because synth bass transients are shorter and sharper than finger-played notes. |
Melodic Instruments — Synths, Keys, Strings, Guitar
Melodic instruments generally need gentler compression than drums and bass. The goal is usually consistency and control — not character. Err on the side of less compression and preserve the dynamic expression of the performance.
Lead Synth
SYNTH| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Classic | 3:1 | 15–25 ms | 80–120 ms | 3–5 dB | Controls peaks without squashing the character. The lead synth should feel dynamic and expressive — not clamped. If you're using the Mix knob (parallel compression at 60–70%), you can push the ratio harder and still keep the natural dynamics. |
Pad / Chord Synth
SYNTH| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Clean | 2:1 | 30–50 ms | 150–200 ms | 2–3 dB | Very gentle. Pads should breathe. Too much compression kills the natural swell and release that makes pads feel spatial and immersive. Clean mode is invisible — you'll barely notice it's there, which is the goal. Long release prevents the pad from "pumping" between chords. |
Piano / Rhodes / Keys
KEYS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Classic | 3:1 | 10–20 ms | 100–150 ms | 3–5 dB | Piano has high transient peaks when keys are struck hard. Compression controls the loudest notes for an even performance — especially useful for sampled pianos where velocity layers can be uneven. Rhodes benefits more from Opto mode for a vintage character. |
Pluck / Arp
SYNTH| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Classic | 3:1 | 5–10 ms | 60–80 ms | 3–4 dB | Tighten the attack consistency across the arp pattern. Individual hits in an arp pattern can vary in level (especially from MIDI velocity). Compression ensures each pluck hits at a consistent level, making the rhythmic pattern feel locked in. |
Strings / Violin Section / Ensemble
STRINGS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Clean | 2:1 | 30–50 ms | 200–300 ms | 2–3 dB | Strings need the longest release times of any instrument. Too short a release and the sustained bowing feels unnatural — the compressor pumps visibly between bow strokes. Use very gentle compression to control the initial bow attack while letting the sustain breathe freely. |
Electric Guitar
GUITAR| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Vintage | 4:1 | 5–15 ms | 80–120 ms | 4–6 dB | Electric guitar benefits from heavy compression. It adds sustain (notes ring longer), evenness, and the vintage FET character of the Vintage mode adds the "snap" that defines classic rock and modern guitar tones. For clean guitars, use Clean mode instead for a more transparent result. |
Acoustic Guitar
GUITAR| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Classic | 3:1 | 15–25 ms | 100–150 ms | 3–4 dB | Moderate comp only. Acoustic guitars should still feel dynamic and alive. Too much compression on acoustic guitar kills the natural pick attack and the "bloom" of the body resonance. Use the Mix knob (70–80%) to blend in parallel compression if you want density without losing the openness. |
Vocals — Lead, Backing Vocals, Ad-Libs
Vocals are the most compressed element in almost every modern production. The dynamic range of a rapper or singer can vary by 20+ dB from whisper to shout. Compression (often in two passes) brings everything to a consistent, intelligible level.
Two-pass serial compression for lead vocals: Use two compressors in series. The first compressor catches the loudest peaks (ratio 4:1, fast attack, 3–5 dB GR). The second compressor adds consistent density (ratio 2:1, slower attack, 2–3 dB GR). The result is smoother than one compressor doing all the work at a high ratio. Less pumping, more natural.
Lead Vocal — Rap / Trap
VOCAL| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Vocal | 4:1 – 6:1 | 5–10 ms | 100–150 ms | 6–10 dB | Heavy compression is normal on rap vocals. The dynamic variation from verse to hook can be enormous. 6:1 ratio and 6–10 dB GR is a reasonable starting point. Vocal mode's programme-dependent behaviour adapts to phrasing automatically. Use two compressors in serial if pumping occurs. Enable SC EQ HP at 100 Hz so low rumble doesn't trigger the compressor. |
Lead Vocal — R&B / Sung
VOCAL| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Vocal | 4:1 | 5–10 ms | 120–160 ms | 6–8 dB | Sung R&B vocals benefit from a slightly longer release (vs. rap) to maintain the smoothness and sustain of held notes. The Vocal mode handles the contrast between quiet verses and loud choruses intelligently. Longer release times prevent the compressor from "pumping" between held notes and phrases. |
Lead Vocal — Melodic / AutoTune
VOCAL| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Vocal | 4:1 – 5:1 | 8–12 ms | 100–140 ms | 6–8 dB | AutoTune / melodic vocals often have uneven gain from pitch processing artefacts. Compression after pitch correction is especially important to smooth out these level inconsistencies. Run the vocal chain: EQ → Pitch Correction → Pro-C3. The compressor sees the final processed signal. |
Backing Vocals / Harmonies
VOCAL| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Classic | 4:1 | 5–10 ms | 80–120 ms | 5–8 dB | BVs need to be consistent so they sit as a solid wall behind the lead. Heavy compression is appropriate here because BVs are background — they should feel dense and consistent, not dynamic and expressive. The lead vocal carries the expression. BVs carry the harmony bed. |
Ad-Libs
VOCAL| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Classic | 6:1 – 8:1 | 3–8 ms | 80 ms | 6–10 dB | Ad-libs jump around dynamically — heavy compression tames them without losing energy. High ratio (6:1–8:1) and fast attack keeps them from jumping out unpredictably. The goal is consistent energy behind the lead vocal, not a featured performance. If an ad-lib still feels too dynamic, automate its volume down by 3–4 dB in the loudest moments. |
Wind & Brass — Flute, Trumpet, Sax, Trombone, Tuba
Wind and brass instruments have wide dynamic ranges — especially when moving between registers or playing from pianissimo to fortissimo. Compression helps control these swings while preserving the "breath" and articulation that make these instruments expressive.
Wind instrument principle: Always use a slower attack than you think you need. The "blowing start" of a wind note is the equivalent of a transient — if you compress it too quickly, the instrument sounds like it has no beginning. Let the attack breathe, then compress the sustain. The Opto or Vocal mode handles this naturally.
Flute / Ocarina (Lead Role)
WIND| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Opto | 3:1 | 20–35 ms | 120–180 ms | 2–4 dB | Opto preserves the breathy, organic quality of flute and ocarina. The slow, programme-dependent release of optical compression lets the sustained note develop naturally before any gain reduction kicks in. Avoid fast attack — it kills the characteristic breath attack of wind instruments. In a supporting role, use half these GR values. |
Trumpet / Lead Horn
BRASS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Vocal | 3:1 – 4:1 | 15–25 ms | 100–150 ms | 3–5 dB | Trumpet dynamics can swing dramatically between registers. Vocal mode is ideal because its programme-dependent algorithm naturally handles the phrasing of a lead brass instrument the same way it handles a singer. Vintage mode works too if you want more character and "blare." |
Alto / Tenor Saxophone
BRASS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Opto | 3:1 – 4:1 | 25–40 ms | 150–200 ms | 3–5 dB | Sax has a wide dynamic range and significant character differences between registers. Opto mode's smooth, slow response preserves the reed character and squawk without clamping. The longer release time prevents pumping between notes and phrases. SC EQ: HP at 150 Hz to prevent the low fundamental from triggering compression on higher notes. |
Trombone (Supporting)
BRASS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Classic | 2:1 – 3:1 | 25–40 ms | 150–200 ms | 2–4 dB | Trombone in a supporting role needs gentle compression. Its low fundamental (82 Hz) can trigger compression disproportionately — use the SC EQ to high-pass at 100–150 Hz so the compressor responds to the midrange character, not the sub energy. Classic mode keeps it transparent and supportive. |
Tuba / Bass Horn
BRASS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Opto | 3:1 | 30–50 ms | 200–300 ms | 3–5 dB | Tuba behaves more like a bass instrument than a brass instrument from a compression standpoint. Treat it similarly to electric bass — Opto mode, slow attack, long release. Use SC EQ to HP at 80 Hz so sub frequencies don't dominate the gain reduction detector. If tuba co-exists with 808/bass, sidechain one to the other. |
Clarinet
WIND| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Clean | 2:1 – 3:1 | 20–30 ms | 120–160 ms | 2–4 dB | Clarinet has a distinctive hollow tone that compression can make worse if overdone. Clean mode, gentle ratio, and a light touch preserve the characteristic wooden resonance. The 250–500 Hz hollow zone should already be addressed in EQ — do not rely on compression to fix tonal problems. |
Brass Section (Ensemble)
BRASS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Bus | 2:1 | 25–40 ms | 150–200 ms | 2–3 dB | Bus the entire brass section and apply glue compression. Individual brass instruments have different attack characters — bussing them together and applying light Bus mode compression makes them breathe as one unified section. When the trumpet peaks, the whole section ducks slightly together, creating cohesion. |
Group Buses — Glue, Consistency & Control at the Group Level
Bus compression is different from track compression. The goal on buses is cohesion — making individual elements feel like they belong to the same group. Less is always more at the bus stage. If you can clearly hear the bus compressor working, it's doing too much.
The bus compression rule: Individual track compression handles peak control and character. Bus compression handles cohesion and glue. Never use bus compression to fix problems that should have been addressed on the individual tracks. If you're pushing 6+ dB GR on a bus, something is wrong upstream.
DRUMS Bus
BUS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Bus | 2:1 | Auto (fastest) | Auto | 2–4 dB | When the kick hits, the whole drum bus compresses — all elements breathe together as one kit. This is the "glue" sound of classic SSL mix buses. Bus mode at 2:1 is gentle but creates a sense of cohesion that makes the kit feel like it was recorded in the same room. Auto attack and release let Pro-C3 handle the rhythmic pumping intelligently. |
BASS Bus
BUS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Limiter | ∞:1 — Hard Limit | N/A | N/A | Safety ceiling −3 dBFS | A safety limiter on the bass bus catches any rogue peaks that survived individual track compression. Set the ceiling at -3 dBFS. Bass instruments — especially 808s on low notes — can have unpredictable sub peaks that clip the master before you notice. This limiter is insurance, not processing. If it's triggering more than occasionally, fix the individual tracks. |
MELODY Bus
BUS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Bus | 1.5:1 – 2:1 | 30 ms | 150 ms | 1–2 dB | Very gentle glue. Melodic elements should feel cohesive, not squashed. The melody bus contains synths, keys, strings, plucks — instruments that should retain their individual character. Barely 1–2 dB GR is enough to create cohesion. If you can hear it obviously working, you are over-compressing the melody bus. |
VOCAL Bus
BUS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Bus | 2:1 | 10 ms | 100 ms | 2–3 dB | Glues all vocal elements — lead, BVs, and ad-libs — into one consistent vocal group. A faster attack than the melody bus (10 ms vs. 30 ms) because vocals are more transient-heavy. The vocal bus should feel like one unified voice, not a collection of separate recordings stacked together. |
PERCUSSION Bus
BUS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Bus | 2:1 | Auto | Auto | 2–3 dB | Light glue so all percussion elements sit at the same perceived energy level. Shakers, tambourines, congas, and bongos can vary significantly in level. Bus compression ensures they form a coherent rhythmic texture rather than individual hits jumping out unpredictably. |
BRASS / WIND Bus
BRASS BUS| Mode | Ratio | Attack | Release | Target GR | Notes |
|---|---|---|---|---|---|
| Bus | 2:1 | 25–40 ms | 150–200 ms | 2–3 dB | Bus your entire brass/wind section together. Apply Bus mode glue compression — when the loudest brass instrument peaks, the whole section ducks slightly, making them feel like one ensemble. Slower attack than the vocal bus preserves the wind instrument breath attack that defines their character. |
Pro Tips — Habits of Experienced Mixers
These are the principles that separate compression that sounds professional from compression that sounds like compression.
EQ before compression — always
The compressor reacts to every frequency it receives. If you haven't cut the mud at 300 Hz yet, the compressor will duck every time that low-mid energy peaks — wasting gain reduction on something you were going to remove anyway.
The bypass test is mandatory
After setting up compression, toggle bypass while keeping makeup gain matched. If the bypassed version sounds more alive and punchy, you are over-compressing. If the compressed version sounds more controlled and even, you have it right.
If you can hear it obviously, it's doing too much
Good compression on buses and melodic instruments is invisible. You only notice it's gone when you bypass it. If you can clearly hear the compressor pumping or ducking on pads, keys, or the vocal bus, reduce the ratio or raise the threshold.
Parallel compression for density without squash
Set the Mix knob to 50–70% instead of 100%. You hear both the heavily compressed version (dense, punchy) and the uncompressed version (dynamic, alive) at the same time. Used on drums, bass, and vocals to add thickness while keeping the transients natural.
Two compressors in series for vocals
First compressor: 4:1 ratio, fast attack, 3–4 dB GR — catches the loudest peaks. Second compressor: 2:1 ratio, slower attack, 2–3 dB GR — adds density. The result is smoother than one compressor at a high ratio. Less pumping, more natural.
Slow attack = preserve transients, fast attack = clamp peaks
Every time you open Pro-C3, ask: do I want the attack of this sound to feel natural and punchy? Slow attack. Do I want consistent, clamped peaks? Fast attack. On drums, almost always slow. On vocals, almost always fast.
Use SC EQ to filter the detection signal
HP the sidechain signal at 80–120 Hz on vocals so low-frequency energy from room noise and breath doesn't trigger the compressor. On bass, HP the sidechain at 150 Hz so the very lowest sub frequencies (which vary a lot) don't cause inconsistent gain reduction.
Auto release is not a shortcut — it's often the best choice
Pro-C3's auto release is programme-dependent and intelligent. For most sources, it avoids pumping better than a manually set release time. Only go manual when you hear a specific problem — breathing between phrases, unnatural sustain — that auto isn't solving.
Match loudness when comparing compressed vs. bypassed
Louder always sounds better to the human ear. If your compressed version is 2 dB louder than the bypassed version, it will always sound "better" — even if the compression is terrible. Set makeup gain so both sound equally loud before judging the compression.
Watch the GR meter, not just the audio
The GR meter in Pro-C3 shows exactly how hard the compressor is working in real time. If it's barely moving, lower the threshold. If it's pegged constantly at -10 dB, raise the threshold or lower the ratio. Target GR should only reach peak values on the loudest moments, not constantly.
Less compression on buses, more on tracks
Individual tracks can handle 4–10 dB GR. Buses should rarely exceed 3–4 dB GR. Bus compression is glue, not correction. If you need to compress a bus heavily, the individual tracks aren't compressed correctly.
Mode first, settings second
Before touching any knob, select the mode. Vintage mode for the kick changes everything about how the attack and release behave compared to Clean mode. The wrong mode with perfect settings will sound worse than the right mode with imperfect settings.