Physical Modelling Synthesis 101 + Super Creative Tips

Physical modelling synthesis is one of the most advanced synthesis types in the game. 

It’s all about recreating real instruments and designing entirely unique sounds by simulating how physical systems behave in real life. 

Plus, successfully fine-tuning parameters, experimenting with excitation sources, and tweaking resonators can give you detailed control over your sound. 

As a producer, learning physical modelling synthesis can seriously level up your skills and give you an edge over the competition. 

That’s why I’m breaking everything down today, like:

• What physical modelling synthesis is ✓
• Key components: excitation, resonators, damping ✓
• Techniques like digital waveguides and finite difference ✓
• Emulating acoustic instruments ✓
• Different synthesis methods ✓
• The best software and plugins ✓
• How to design custom musical instruments ✓
• Mixing real and hybrid models ✓
• Advanced tips for unique sounds ✓
• Putting a spin on conventional instruments ✓
• Creative production/sound synthesis techniques ✓
• Much more about physical modelling synthesis ✓

By understanding physical modelling, its functions, and advanced techniques, you can add new dimensions to your sound design. 

Plus, you’ll help your tracks stand out with lifelike tones, expressive textures, and experimental sounds. 

This way, you’ll elevate your production game and create music that feels authentic and innovative like a boss.

What is Physical Modelling Synthesis?

Physical modelling synthesis is a revolutionary synthesis technique that recreates the sounds of acoustic instruments.

It does so by simulating how their physical characteristics interact in real life. 

Instead of relying on traditional waveform-based synthesis or sampling, it uses mathematical models to simulate acoustic systems like: 

• Strings
• Tubes
• Resonators
• Etc.

This replicates how a real instrument behaves when played, including details like vibrations, resonant frequencies, and even imperfections. 

For example, think of a plucked string… Physical modelling doesn’t just simulate its pitch but also the way it vibrates, decays, and interacts with its surroundings. 

This allows you to go beyond imitating real-life sounds and opens the door for you to create unique sounds that blend realism and creativity in a really cool way.

It’s an exciting method for anyone who wants to push the boundaries of digital synthesis like myself.

All while maintaining the expressive qualities of musical instruments.

Basic Principles of Physical Modelling

Physical modelling is all about mimicking how sound waves interact with the components of a physical system like strings, membranes, or air columns. By breaking down these interactions into mathematical models, you can successfully simulate the parameters that make a musical instrument work in a natural, expressive way. Let’s kick things off with the key components.

• Key Components

In physical modelling synthesis, every sound starts with an interaction between the three main components:

1. Excitation source
2. Resonator
3. Damping mechanism

The excitation source represents how energy is added to the system, like a plucked string, a virtual bow sliding across a string, or air blown through a brass instrument. 

The resonator is where the sound waves take shape, amplifying certain resonant frequencies based on the physical structure of the simulated instrument. 

For example, simulating the hollow body of a guitar or the tube of a flute shapes how the sound resonates and decays. 

The damping mechanism controls how energy is lost over time 一 simulating the natural decay of a sound to perfection.

This can mimic anything from a string instrument’s gradual fade to the sharp muting of a mallet instrument. 

By combining these elements, physical modelling algorithms allow us to recreate highly realistic acoustic instruments and even design hybrid instruments that don’t exist in the real world. 

I bet the wheels in your head are already starting to turn, am I right?

When tweaking parameters like delay time, feedback level, and resonance, you can go from recreating a real instrument to producing unique sounds that are entirely your own.

Don’t worry, we’ll break it all down a little further in the article.

• Excitation Sources 

The excitation source as we just touched upon is where the magic begins in physical modelling synthesis. 

It’s all about adding energy to the physical system 一 just like striking, plucking, or blowing into a real instrument. 

For example, you can simulate the pluck of a string or the buzz of a reed using a noise source paired with precise controls over attack and energy distribution. 

Or, recreate the strike of a piano hammer on a string by adjusting the parameters to reflect the strength of the strike and where it contacts the string. 

It all depends on what you’re aiming for, of course.

On the same note, in digital waveguide synthesis, the excitation source often incorporates filtered noise or pulses to simulate how a performer interacts with the instrument itself.

For creative sound design, consider layering multiple sources, like blending a virtual bow with a mallet strike for new sounds that are both percussive and sustained.

PRO TIP: Control the feedback level of your excitation source to shape the dynamics, especially if you’re aiming for expressive results like the breathiness of a flute or the sharp attack of a drum. 

The more detailed you get with these parameters, the more you can manipulate energy to create sounds that are both realistic and experimental.

• Resonators

Up next we have the resonator, which is the part of a physical modelling synthesizer where raw vibrations from the excitation source are shaped into a defined, tonal sound. 

For example, when simulating the hollow body of a guitar, set the resonance frequency around 300-400 Hz to emphasize the warm, natural characteristics of the wood. 

If you’re working on a flute, adjusting the delay line to roughly 25-35 ms can recreate the reflective qualities of the air column inside the tube. 

For more control over brightness, use a low-pass filter after the resonator with a cutoff around 8 kHz and a resonance of 0.6.

This will smooth out any harshness in the high frequencies. 

With percussive instruments like virtual drums, tweaking the boundary conditions can create more realistic or creative results.

Try setting the feedback level at 0.8 to simulate a tightly tuned drumhead. 

Hybrid designs are where resonators really shine, though…

Ending the tonal warmth of a string body with the sharp resonance of a metal tube can produce unique sounds that feel both familiar and futuristic (the perfect balance).

NOTE: To fine-tune things, play around with the damping settings to let the sound waves resonate longer or fade quicker depending on the effect you’re going for.

• Damping Mechanisms

And the last of the key principles we have the damping mechanism in a physical modelling synthesizer, which controls how energy dissipates over time.

This directly affects how realistic or dynamic your particular instrument sounds. 

For example, with a plucked string, setting the damping coefficient around 0.01-0.03 simulates a natural, gradual decay.

Increasing, on the other hand, it to 0.05 produces a sharper, more muted sound. 

To recreate the soft fade of a drumhead, apply light damping with a resonance parameter of 0.4 and adjust the feedback level to 0.85 for a balanced decay. 

If you’re designing a wind instrument, like a virtual saxophone, add a touch of noise source during the damping phase to simulate breathiness.

This makes sure it fades naturally by setting a high-frequency cutoff at 6 kHz. 

For more creative applications, you can mess around with extremely low damping to let the sound sustain almost indefinitely, great for atmospheric pads or soundscapes. 

A low-pass filter with a cutoff around 10 kHz and a slope of -18 dB/octave can help smooth out any unnatural artifacts during decay. 

My advice is to test the damping parameters in different types of contexts.

Slower damping is ideal for expressive solo instruments, while faster damping works well for rhythmic, percussive sounds. 

Just keep in mind that damping isn’t just about realism 一 it’s a key to shaping unique sounds that stand out in your mix.

Techniques in Physical Modelling Synthesis

To get the absolute most realistic and expressive sounds, you have to mess around with different techniques that simulate the behavior of acoustic instruments. This could be digital waveguide synthesis, finite difference methods, and mass-spring models, which we’re breaking down in the following sections. Let’s get into it.

• Digital Waveguide Synthesis

Digital waveguide synthesis is one of the most popular and efficient methods in physical modelling synthesis, especially for simulating string instruments and wind instruments. 

To recreate how sound waves travel through a certain medium (like a vibrating string or air column), it uses a mix of:

• Delay lines
• Filters
• Feedback loops

For example, simulating a guitar string often involves a delay line of about 10-40 ms to represent the length of the string.

With a low-pass filter applied to mimic the natural energy loss over time as we learned in the previous section.

If you’re working on a flute model, you can use a resonant low-pass filter with a cutoff frequency around 5 kHz and a feedback coefficient of 0.7 to replicate how air vibrates and dissipates within the instrument.

A key feature of this technique is its efficiency… You can simulate multiple strings or resonators using relatively few computational resources. 

To kick things up a notch when it comes to realism, experiment with adjusting the feedback level and filter resonance to control how the sound evolves.

You could, for example, add a subtle attack phase for plucked instruments. 

My advice is to use waveguide synthesis when you need highly detailed yet computationally efficient models.

And keep in mind that it’s very useful for real-time performance or CPU-heavy sessions.

If you’re looking to design hybrid instruments, try blending waveguide-based strings with other resonant systems, like metallic tubes.

This will produce unique sounds with both realism and creative flair, which I personally find super intriguing (and your audience probably will as well).

PRO TIP: Make sure to fine-tune the delay time and filter slope when creating layered or multi-string sounds to avoid phase inconsistencies.

• Finite Difference Methods

Finite difference methods are a more advanced way of physical modelling synthesis, giving you the flexibility to simulate the behavior or more complex acoustic systems.

Unlike digital waveguide synthesis, which uses predefined feedback loops, this method calculates how each point of a physical structure (like a string or drumhead) interacts with its surrounding elements using mathematical models. 

And if you’re starting to get a little overwhelmed, the plugins you use will do all the math for you, don’t worry.

For example, when creating a virtual string instrument, you can define the material properties of the string, such as its tension and mass.

You simply set parameters like the stiffness coefficient to 0.1-0.3 for natural vibrations. 

If you’re emulating a drumhead, use a grid-based structure with a frequency damping factor of 0.05-0.08 to d realistic energy dispersion. 

While this technique demands more processing power, it excels at recreating nuanced details like nonlinearities or edge effects.

It’s perfect for so many different real-life behaviors like the snapping of a plucked string or the gradual energy loss in mallet instruments. 

To make the most of this method, focus on balancing the grid resolution and time step 一 smaller values offer more precision but can increase CPU load, naturally.

I suggest you use finite difference methods when you’re aiming for MAX realism and are willing to invest the extra computational power for highly detailed simulations. 

NOTE: If you’re feeling froggy, adjust the boundary conditions to simulate unusual surfaces, such as a virtual membrane made of glass or a hybrid material, to explore new sounds and textures.

• Mass-Spring Models

Mass-spring models are super useful when it comes to simulating how objects vibrate and interact in physical modelling synthesis. 

This method breaks down a structure, like a string or drumhead, into smaller parts: 

• Masses (representing points of the object)
• Springs (defining how those points connect and move)

For example, when recreating a plucked string, you can set the spring stiffness between 0.2-0.4 to capture realistic tension.

While, at the same time, adjusting the mass values depending on whether you’re simulating nylon or steel strings. 

If you’re designing percussion (like a virtual drum) play around with the damping coefficient; a setting of 0.1 gives a soft, natural fade, while 0.3 creates a sharper decay.

 

One trick I use all the time is combining this simple model with a low-pass filter (cutoff around 7-8 kHz) to smooth out unwanted harshness from high-frequency artifacts. 

You can even go beyond realism by tweaking the spring settings to simulate materials that don’t exist in real life, like metallic rubber or glass strings.

So, if you’re looking for unique sounds that sound super futuristic, this is perfect.

NOTE: This takes a little more setup, but it’s perfect for producers like yourself who want precise control over their sound design.

• Pro Tip: The Best Physical Modelling Software & Plugins

When it comes to physical modelling synthesis, choosing the right plugins/software can make all the difference if you really want realistic, expressive sounds. 

My 2 favorite plugins for this purpose are:

• Modartt Pianoteq, known for its stunningly detailed piano models.
• Audio Modeling’s SWAM instruments, which excel at replicating acoustic instruments like strings and brass. 

For more experimental sounds, Applied Acoustics Systems’ Chromaphone allows you to combine resonators and excitation sources to knock out crazy sounds.

If you’re into building custom models from scratch, Max/MSP is pretty impressive and powerful.

It lets you define every aspect of the physical system using physical modelling synthesis algorithms and even tweak parameters in real-time. 

A great free option is Dexed, which uses some elements of digital waveguide synthesis for recreating percussive and plucked tones. 

For added control, look for plugins that support MIDI CC mapping 一 this lets you assign things like velocity or aftertouch to specific parameters (damping or resonance). 

My advice is to test out a few plugins with trial versions and start with presets.

Then, tweak the delay time, feedback level, or low-pass filter settings to get a feel for how each plugin handles the interaction between excitation sources and resonators.

Bonus: Creative Physical Modelling Synthesis Techniques

#1. To take your tracks (and skills) to the next level with physical modelling synthesis, start by tweaking physical characteristics to create unexpected variations. 

For example, when emulating a string instrument, slightly increase the damping coefficient to produce a muted, lo-fi effect.

Or, reduce the resonant frequency to emphasize deeper, darker tones. 

#2. You can mix up different resonators and excitation sources to design hybrid instruments.

For example, pair a cello’s wooden resonance with the metallic attack of a vibraphone for a unique texture or something like that 一 dealer’s choice.

#3. Use waveguide synthesis to experiment with evolving effects by adjusting the feedback level dynamically during performance.

This lets the generate sound evolve over time. 

#4. Throwing in subtle noise sources, like filtered white noise, can add realism to wind instruments or give percussion a somewhat ‘gritty’ edge. 

#5. For percussive sounds, fine-tune the delay time (10-20 ms) to control the tightness and overall impact of hits. 

#6. Layer unconventional boundary conditions, like unevenly stretched virtual membranes, to create sounds that shift unpredictably.

It can give your tracks a lively, organic feel that really works out well.

These techniques not only enhance realism but also open up creative possibilities for new sounds that feel super unique and expressive.

Final Thoughts

Physical modelling synthesis isn’t the easiest technique to master, but that’s what makes it so epic (and seriously fun). 

It’s all about simulating the intricate behaviors of real-world instruments and designing unique sounds that push all creative boundaries. 

Plus, by carefully adjusting parameters like excitation sources, resonators, and damping mechanisms, you can achieve a level of expressiveness that blows minds.

Using the physical modelling synthesis techniques and insights we’ve covered, you’ll be able to use physical modelling synthesis like a true professional.

As a special bonus, since we talked about percussion, you should really check out these legendary Free Percussion Samples pack. 

It includes 20 expertly crafted percussion sounds 一 ranging from crisp snares to warm congas that are all perfect for adding unmatched texture/depth to your tracks. 

These samples are perfect for working with physical modelling synthesis, as they blend flawlessly with virtual instruments to create hybrid and layered grooves. 

The sounds are clean, dynamic, created by pros, and ready for use in any genre.

You’ll have a powerful starting point for experimenting with rhythmic ideas inspired by this synthesis technique.

Bottom line, mastering physical modelling synthesis takes time, but it opens up limitless possibilities for your tracks to really dominate the competition.

So, make sure to always curious, keep experimenting every sing day, and let your creativity shine through every sound you design.

Until next time…