Saturation and distortion: overview

What it is and how it works

Saturation and distortion belong to the same family of processes: a nonlinear transfer curve (waveshaping) makes the output no longer proportional to the input. As the signal approaches the limit, the peaks are rounded off (soft clipping) or cut off (hard clipping). This deformation creates new harmonics, multiples of the frequencies present, and intermodulation (sums and differences between different frequencies).

• Saturation: little deformation, low and soft harmonics, an effect of warmth, density, presence. It often isn't "heard" as distortion, but the sound seems louder and closer.
• Overdrive: obvious deformation but still musical, dynamic (it depends on how hard you push).
• Distortion/fuzz: strong deformation, many harmonics, heavy compression.
• Digital lo-fi (bitcrusher, decimator): not analog waveshaping, but a reduction in resolution or sample rate: quantization noise and aliasing.
• Wavefolder: instead of cutting, it "folds back" the waveform beyond the threshold: rich, metallic harmonics.

Even and odd harmonics

• Symmetric curves (same treatment for the positive and negative half-wave) create mostly odd harmonics (3rd, 5th, 7th): harder, "squarer" sound, typical of transistors, clippers, fuzz.
• Asymmetric curves also create even harmonics (2nd, 4th): the 2nd is the octave above, the 4th two octaves: warmer, "fuller" sound, typical of single-ended tubes and tape (tape actually produces mostly 3rd harmonic, but with soft compression).
• Many plugins have a symmetry/bias control (Fruity Delay 3 in the Feedback Distortion section; Saturn 2; Decapitator with "Punish"). Shifting the bias also generates a DC offset: remove it with an HP at 10–20 Hz or with Fruity Center / DC block.

Why saturate in a mix

• Audibility on small speakers: an 808 at 45 Hz doesn't exist on a phone; its harmonics at 90, 135, 180 Hz do (the "missing fundamental" effect: the brain reconstructs the note). FL Studio's Low Lifter is made for this.
• Density and loudness: rounds off the peaks (less crest factor) without the pumping of a compressor.
• Presence: harmonics in the upper mids bring vocals and synths forward without EQ.
• Cohesion: light saturation on buses and master glues the elements together ("console" and "tape" effect).
• Character: guitars, basses, leads, aggressive drums.

Common parameters

• Drive / Input: how far you push into the curve. It is the main parameter.
• Output / Trim: compensates the volume (saturation raises the perceived level).
• Mix: parallel, essential for dosing transparently (20–50% on a bus).
• Tone / Tilt / pre and post filters: filtering before reduces intermodulation (e.g. low-pass before the distortion on guitar; Pre Band and Post Filter of Fruity Blood Overdrive), filtering after removes harshness.
• Type/curve: tape, tube, transistor, diode, hard clip, foldback, bitcrush.
• Oversampling: 2×–16×. Distortion generates harmonics above Nyquist that "bounce" back down as aliasing (non-harmonic, dirty frequencies). Oversampling reduces them; it costs CPU and latency.
• Bands: multiband saturation (Saturn 2, Frequency Splitter + different saturators) to saturate the mids of the 808 without touching the sub.

Map of types (dedicated guides)

Tools in FL Studio

• Fruity Blood Overdrive (Pre Band, Color, Pre Amp, x100, Post Filter, Post Gain): simple and useful overdrive.
• Distructor: 4 slots with Distortion, Filter, Chorus, AMP/CAB modules; Blood Overdrive, Soft Clipper, Harmor (Classic, Flathat, Cube, Log, Softsat, Rubber, Ribbon, Sincrush, Bitcrush, Bitjam), Distructor (Wave folder, Aperture, Abrasive), Crusher (Rate Crush, Bit Crush) models.
• Fruity WaveShaper: drawable curve (you can create any saturation, even foldback).
• Fruity Fast Dist, Fruity Squeeze (bit reduction and "Puncher"), Effector (DISTORT, LO-FI), Hardcore (guitar multi-effect), Fruity Soft Clipper, Soundgoodizer/Maximus (per-band saturation), Low Lifter (harmonics on the bass), Fruity Delay 3 (saturation and limit in the feedback).
• Third party: FabFilter Saturn 2, Soundtoys Decapitator and Radiator, Waves J37/Kramer Master Tape/Abbey Road Saturator, UAD (Studer A800, Ampex ATR-102, Neve, API), Softube Tape, iZotope Trash, Klanghelm IVGI (free), Camel Crusher (free), Kilohearts Distortion.

How much and where

• Single track: from barely perceptible (mix 20–30%) to obvious (guitars, 808, lead).
• Bus: light saturation, 1–3 dB of peak reduction, mix 30–60%.
• Master: very light (tape or console), or a clipper before the limiter.
• Order: saturation before the compressor = the compressor controls the harmonics and the resulting dynamics; after = the saturation rounds off the peaks that the compressor lets through. Both are valid: choose by ear.

Common mistakes

• Saturating everything a little: each stage adds harmonics in the upper mids; in the end the mix is harsh and fatiguing.
• Not compensating the volume: saturation always seems better because it is louder.
• Saturating the sub of an 808 or a kick: intermodulation and mud. Saturate the harmonics (band above 80–100 Hz) and leave the sub clean.
• Forgetting aliasing on heavy distortions at 44.1 kHz: turn on oversampling.
• Asymmetric bias without an HP: DC offset that eats headroom.

How to hear it

• Raise the drive until you clearly hear the distortion, then back off until it "disappears": that point is saturation.
• At matched volume, listen in mono on a small speaker: the saturated instrument stays audible.
• Analyzer: with a sine tone (e.g. 100 Hz) you see the harmonics appear at 200, 300, 400 Hz: you can tell whether the plugin produces even or odd ones.