Definition
Physical modeling synthesis does not reproduce an instrument's waveform but simulates its physical operation: an exciter (pick, hammer, bow, breath) sets a resonator (string, tube, membrane, plate, soundboard) into vibration, described by equations or digital models. The result reacts naturally to touch: playing harder doesn't just raise the volume, it changes the timbre as in a real instrument.
Essential history
- Karplus-Strong (Kevin Karplus and Alex Strong, 1983): a short burst of noise enters a delay line as long as the note's period; on each pass the signal goes through a low-pass filter (an average between samples). Result: a surprisingly realistic plucked string with very little computation.
- Digital waveguides (Julius O. Smith III, Stanford CCRMA): generalization with bidirectional delay lines that model strings and tubes.
- Yamaha VL1 (1994): first commercial physical modeling synth for winds and strings, very expressive but expensive.
- Today: Modartt Pianoteq, AAS Chromaphone and String Studio, Ableton Collision, Tension and Electric, Arturia Piano V (physical model, in the V Collection 9), Native Instruments Reaktor Prism, the string/resonator models of Pigments and Vital.
Components of a model
- Exciter: type (impulse, noise, continuous bow, breath), hardness, position (plucking near the bridge = more high harmonics), force.
- Resonator: type (string, open/closed tube, membrane, bar, plate), tuning, damping (decay), stiffness (inharmonicity: piano strings have slightly stretched partials), material (wood, metal, glass).
- Coupling and body: the soundboard and sympathetic resonators (piano strings with the pedal down).
- Nonlinearities: beating, mechanical noises, saturations.
Why use it
- Expressiveness: velocity, aftertouch, MPE and mod wheel change the physical behavior; ideal with MPE controllers (Roli, Linnstrument, Osmose).
- Lightness: no gigabytes of samples (Pianoteq weighs a few tens of MB).
- Impossible hybrids: a string excited by a bow with a glass body; tuned “metallic” percussion for futuristic pads and plucks.
Basic recipes
- Karplus-Strong pluck: short noise (5 ms) → tuned delay → low-pass. The darker the filter, the shorter and duller the sound; higher feedback = longer sustain.
- Mallet / marimba: soft impulsive exciter on a wooden bar, decay 0.5–1 s, moderate inharmonicity.
- Bowed string (pad): bow with pressure modulated by a slow LFO, cello body, reverb.
- Metallic percussion: metal bar or plate, high inharmonicity, long decay: synthetic bells and gongs.
In FL Studio
FL Studio has no true dedicated stock physical modeler like Collision, but you can build a “homemade” Karplus-Strong: a short noise burst (3x Osc with a short envelope) sent to Fruity Delay 3 or a comb filter with a delay of a few ms and high feedback: by tuning the delay time to the note (1000 ÷ frequency ms: A3 = 220 Hz → 4.55 ms) you get a string. For complete instruments use Piano V, Pianoteq, Chromaphone.
Example in A minor
Metallic pluck for an ambient track at 90 BPM: in Chromaphone (or similar) hard mallet exciter, “beam” resonator with medium inharmonicity, decay 1.2 s; arpeggio A3 – C4 – E4 – B4 on Am(add9) and F – A – C – E on Fmaj7 in eighth notes; delay at dotted 1/4, reverb 3 s. Piano V with close mics for the chords.
Common mistakes
- Expecting absolute realism: the models are convincing in the mix, less so soloed on winds and voices.
- Ignoring velocity: it is precisely the strong point.
- Excessive feedback and resonance values: self-oscillation and peaks (put a safety limiter on while experimenting).
Exercise
- Build a Karplus-Strong with noise + tuned delay + filter in FL Studio and play C4 (3.82 ms delay) and A3.
- With Piano V, compare velocity 40 and 110 on the same note: note what changes in the spectrum with an analyzer.
Connections
“Sampling and samplers”, “Additive synthesis”, “Pluck design”, “Filters”, “The harmonic series and timbre”.