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What is Ring Mod, FM, and Amplitude Modulation?

Modulation is a fundamental technique used in electronic music to create interest, complexity, and variation in the sound. Modulation refers to the process of changing the sound's parameters over time, such as pitch, filter cutoff, or amplitude, to create dynamic and evolving soundscapes.

Here are some reasons why modulation is so important in electronic music:

  • Adds Interest and Variety: Modulation allows electronic music producers to create interest and variety in their music by adding movement and evolution to their sounds. Without modulation, the sound can become static and repetitive, making it less engaging for the listener.
  • Creates Tension and Release: By using modulation to gradually increase or decrease certain sound parameters, electronic music producers can create tension and release in their music. This can add emotion and drama to a track and make it more engaging for the listener.
  • Enhances Sound Design: Modulation is essential to sound design in electronic music, as it allows producers to sculpt unique sounds and textures. By modulating the different parameters of a synthesizer, for example, producers can create complex and evolving sounds that are difficult to replicate using acoustic instruments.
  • Enables Automation: Modulation allows producers to automate various sound parameters, such as filter cutoff, LFO rate, or delay time, using MIDI or automation tools in a DAW. This makes it easier to create complex and evolving sounds, and allows producers to focus on other aspects of music production, such as arrangement and composition.

Overall, modulation is a key aspect of electronic music production, and mastering this technique is essential for creating engaging and dynamic tracks.

Let's start with frequency modulation (FM)

Frequency modulation (FM) is a type of audio processing that can be used in music synthesis to create a wide range of interesting and unique sounds. Frequency Modulation is the technique of using one oscillator's frequency (modulator) to modulate the rate of another oscillator's frequency (carrier) often used in conjunction with an attenuator to control the amount of modulation from the modulator source.

In FM synthesis, an audio signal is used to modulate the frequency of a synthesized waveform, such as a sine wave or a square wave. This can create complex timbres and tonal effects, depending on the shape of the waveform and the characteristics of the modulating signal.

FM synthesis is often used to create percussive sounds, such as those produced by a piano (Yes, the piano is considered a percussive instrument) or a marimba. FM synthesis can also be used to create other types of sounds, such as bells, chimes, and metallic noises.

Unlike other forms of synthesis, such as subtractive synthesis or additive synthesis, FM synthesis allows for a great deal of control over the timbre of the resulting sound. Small adjustments go a long way with FM synthesis. This makes it a powerful tool for musicians and sound designers, who can use it to create a wide range of sounds that are difficult or impossible to achieve with other synthesis methods.

Frequency Modulation example
Frequency Modulation​​, Wikipedia

Some history for context

The use of frequency modulation (FM) for synthesis originated with the work of John Chowning, an American composer and researcher, in the late 1960s and early 1970s.

Chowning was interested in creating complex sounds with electronic synthesizers, and he began experimenting with the idea of using FM to generate new timbres. He discovered that by using one oscillator to modulate the frequency of another oscillator, he could create rich and dynamic sounds that were difficult to produce with other synthesis techniques.

John Clowning
John Chowning, Wikipedia​​

Chowning developed a mathematical model for FM synthesis, which he published in a series of papers in the 1970s. He also worked with Yamaha to develop the first commercial FM synthesis instrument, the Yamaha DX7, which was introduced in 1983 and became one of the most popular synthesizers of the 1980s.

The success of the DX7 and other FM synthesis instruments led to the widespread use of FM in electronic music, particularly in genres such as pop, rock, and electronic dance music. FM synthesis has since been used to create a wide range of sounds, from bell-like tones to growling basses, and continues to be a popular synthesis technique in modern music production.

Yamaha DX7

In Eurorack format frequency modulation (FM) is an easy ask. Almost all oscillators or filter modules will have an FM input and if it doesn't you can mix your pitch source together with your FM source using a buffered summing mixer. Just make sure you run the FM source into an attenuator first so that it doesn't get too wild! 

A simple patch to try is a "vibrato" patch. Plug your LFO output, preferably a triangle (if you want to be a traditionalist) into your oscillators FM input and adjust the signal depth to taste. Vibrato typically sits at or below 20hz.

Patchwerks Modular System

About ring modulation

Ring modulation is a sound processing technique that has been around for over 100 years. It was first used in the early 1900s to send audio signals over radio waves. Back then, radio equipment wasn't at all what it is today and the available bandwidth was limited. Ring modulation was an innovation that allowed both voice and data to be sent over a single radio frequency, which helped save bandwidth and improve transmission quality.

After the Second World War, people in the music industry started to experiment with ring modulation as a way to create unique and interesting sounds. By the 1960s, it had become a popular technique in electronic music, and was used by artists like Karlheinz Stockhausen.

Technical Talk: Ring Modulation combines two audio input signals to create an enitrely new signal. In a ring modulator, the two input signals are mixed together using a ring of diodes, a diode is an electronic component that allows current to flow in only one direction. The resulting output signal has a frequency that is the sum and difference of the frequencies of the two input signals. For example, if one input signal has a frequency of 100 Hz and the other has a frequency of 300 Hz, the output signal will have a frequency of 400 Hz (the sum of the input frequencies) and a frequency of 200 Hz (the difference of the input frequencies).The resulting output signal will be a combination of these two frequencies, with the amplitude of each frequency being determined by the amplitudes of the input signals. This can create a range of interesting and unusual sounds.

Ring Modulation waveforms
Ring Modulation, Wikipedia​​

Let's look at amplitude modulation

Amplitude Modulation waveforms
By Ivan Akira - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=9820131​​

Amplitude modulation (AM) can be used in music synthesis to create a range of interesting and unique sounds. In this application, an audio signal is used to modulate the amplitude of a synthesized waveform, such as a sine wave or a square wave. This can create a wide range of timbres and tonal effects, depending on the shape of the waveform and the characteristics of the modulating signal.

One common use of AM in music synthesis is to create the "wah-wah" sound often heard in electric guitar effects. In this case, a low-frequency oscillator (LFO) is used to modulate the amplitude of the guitar signal, resulting in a sweeping effect that can be controlled by the musician. AM can also be used to create other types of effects, such as tremolo, vibrato, and phasing.

Amplitude modulation is a something you can do very easily with a VCA (voltage controlled amplifier) and an oscillator (HFO or LFO). Simply plug in the oscillator output into the VCA's CV input and play with your oscillators frequency control. Higher speeds will create more artifacting and harmonics, resulting in a unique and distorted sound.

LET'S recap

Ring Modulation: Ring modulation is a technique where two sound waves are combined through a ring modulator to create a new, more complex sound. This technique can produce a wide range of interesting and unique sounds that are often used in electronic music, such as robotic or metallic sounds.

Frequency Modulation: Frequency modulation is a technique where the frequency of one sound wave is modulated by another sound wave. This technique can produce a rich and complex sound with a lot of harmonic content, making it great for creating sounds like bells or electric pianos. 

Amplitude Modulation: Amplitude modulation is a technique where the amplitude (or volume) of one sound wave is modulated by another sound wave. This technique can produce a variety of interesting sounds, from distorted guitars to electronic percussion. 

Overall, these modulation techniques are valuable in electronic music because they allow producers to create unique and interesting sounds that can't be achieved with traditional instruments. By combining different waves and manipulating their properties, electronic music producers can create a vast array of sounds that push the boundaries of what's possible in music. So, the next time you listen to electronic music, try to listen for these different modulation techniques and see if you can hear how they're used to create the sounds you're hearing!

Matthew Piecora

Matthew Piecora, aka EZBOT, is a Seattle-based artist and educator, who specializes in hardware electronic music. In his compositions you’ll discover sounds inspired by 90’s alternative rock, deep house, techno, and jazz. Using experimental live-coding, samplers, synthesizers, and complex sequencers, EZBOT aims to evoke feelings of nostalgia using modern music technology.