Basic Synthesis and Sound Design essentials:
I wanted to give you some basic concepts to synthesis that you can quickly use to better your sound design abilities. My hope is that I am able to help people who haven’t yet had the ability to grasp it quite yet. I will do my best to share what I understand in a way that is easily digestible. This stuff has taken me years to understand. With any luck, this will shave a lot of time off of your learning curve. Feel free to correct me if you find more useful or more simplistic definitions for the following terms.
Waveforms
Sine wave – The simplest of all waveforms. It has no harmonics so is quite pure in sound. a Sine wave is best used for Sub-bass.
Square wave – This waveform only exsists as highs or lows with nothing inbetween. It’s produced by only odd harmonics which gives a more hollow sound. Good for creating wind instrument tones, widening strings and pads and deep wide bass tones.
Pulse wave – This is basically like a Square wave with adjustable highs and lows which can vary the harmonic content of the sound. can create reed like tones.
Sawtooth Wave – Produces all odd and even harmonics which is great for raspy dirty tones as well as brassy sounds. Also good for lead sounds and in your face bass tones.
Triangle wave – This only contains odd harmonics and is great when mixed with Sine, Square or Pulse waves to add some brightness or glitter.
Noise wave – A random mix of all frequencies instead of actual tones. White noise has an equal amount of amplitude throughout the frequencies which Pink noise has differing energies giving it a perceived deeper tone.Noice waves are excellent for percussive sounds (especially snare and handclaps) as well as wind or ocean sounds.
Additive Synthesis:
If you are using a waveform that is more complex than a simple Sine wave, then you are using a form of Additive synthesis. Anytime you add harmonic content to a wave to create a Saw, Square, Triangle or Pulse wave, you are using Additive synthesis. When you see wave options that say, for example, Saw 16, Saw 32, and Saw 64, just know that the higher the number (16, 32, 64 etc), The more high frequency harmonics have been added to the sound. You may want to think of this as fuller or brighter in tone.
Oscillators:
An oscillator is basically a sound generator. This oscillator generates a Sine wave in its most basic form. Square, Triangle and Saw waves are all derivative of the Sine wave. The only difference are the harmonics added to the sound at different frequencies and amplitude (volume) levels. The process of adding harmonic frequencies to a sine wave is called Additive synthesis.
Lets use the Operator instrument as an example…
The Operator instrument has 4 Oscillators, meaning 4 simple sound generators, which can by mixed together in a number of ways to create a final sound. Operator offers both Subtractive and FM synthesis algorithms.
One approach would be to to make 4 separate waveforms and mix them together(This could also be a form of Additive synthesis). This would give you more predictable results as you can fairly easily distinguish each separate sound of each oscillator that creates your completed sound. In it’s most basic form, this is similar to having a 4 track recorder and simply mixing each instrument together to make a song by adjusting the volume and a few other parameters.
Envelopes:
Any thing that happens to a sound over time involves envelopes. Amplitude(volume), Oscillators and filters all have Envelopes as can pitch. Each of these Envelopes can be completely different within one sound which can drastically influence the final sonic results.
In any sound or effect there are 4 components over time that make up an envelope. We will use an amplitude envelope as an example:
Attack – how quickly a sound reaches it’s peak level after a key is hit to trigger the sound
Decay – how quickly a sound drops to a level that it will remain at after the Attack peak. Sometimes the sound will remain at it’s peak level. Other times the sound will jump up quickly in volume and then settle at a lower volume.
Sustain – The level that that sound remains at after the decay until the key is released (this is a volume setting not a time setting)
Release – How quickly the sound level fades to nothing after the key is released.
Since each sound can have multiple envelopes, a sound can get really complex, but that doesn’t mean the building blocks of these sounds can’t be made from a basic knowledge of synthesis.
Subtractive Synthesis:
Subtractive synthesis is a model of sound design where you chip away at the frequencies of a simple or complex waveform with a filter (Complex waveforms being the result of additive synthesis, or, the adding of harmonics to a simple sine wave). You are subtracting certain frequencies from a rich, full range sound to create a tone you find satisfying. You can think of subtractive synthesis sound design in a similar way to how a sculptor creates his art. The “art” is already their, he just needs to chip away what isn’t needed.
FM Synthesis:
With this approach, the results of how each oscillator will effect your final sound is less predictable. Basically FM synthesis uses 1 oscillator as the main sound and each other oscillator as a waveform that modulates the first sound. This combination makes for much more complex results. You can look at subtractive synthesis like a salad. In a salad you have a combination of vegetables but with all it’s separate parts completely recognizable. FM synthesis is more like baking a cake. The sum of each ingredient may result in something that looks nothing like the original raw ingredients. The math involved would make your head spin, so just trust me on this. Another way to look at it is that subtractive synthesis is like a mixture of wet and dry signal on a reverb whereas FM synthesis is like having the reverb set to 100% leaving none of the original signal. This isn’t the perfect analogy however as Subtractive synthesis can be a mixture of several tones whereas classic FM synthesis is the processing or modulating of one single tone.
With FM synthesis you will need to rely on experimentation in order to build a vocabulary of familiar combinations. If you have never heard what a square wave sounds like when it is modulated by a triangle wave, which in turn is being modulated by a saw wave, you won’t be able to predict in your head the outcome. Do not feel like an idiot that you can’t simply think of a sound in your head and bang it out using fm synthesis. It’s going to take some time to understand how one waveform alters the sound of another. For now, just clear your mind and mess with the oscillators until something sounds cool, then take note of how you created it. You’ve now built your vocabulary. Repeat this step until you can start to predict how something will sound. Then you will move to a combination of predicting and experimenting.
Whereas with Subtractive synthesis frequencies can be altered with a filter, FM synthesis can create rich harmonics when one oscillator is modulated by one or more other oscillators. It is advisable to start with a darker tone and build the harmonic frequencies with other oscillators and then use the filter at the end if desired. The use of a filter on FM synthesis is supposedly not necessary since modulating oscillators can do that for you and classic FM synthesis doesn’t involve a filter. The use of a filter is kind of a mixture of FM and Subtractive synthesis.
Other forms of synthesis:
Other forms of synthesis includes:
Granular synthesis which uses a sequences of short grains(waveforms) to form a longer output sound.
Physical Modeling which uses some very complex mathematics and waveforms to create a realistic sound of wind a drum hit or bowed instruments.
Wavetable Synthesis which is usually made with a small collection of waveforms spliced together and looped. These loops can be measured in milliseconds. Think of it as microscopic audio samples mixed together to create a complex texture.
I’m not going to dive any further into those as my goal was to help you dive into the basics of synthesis. If you would like to really elevate your sound design skills, I highly recommend you purchase the Sampler or Operator video collections by Nick Maxwell at www.NicksTutorials.com. Much of what I am sharing with you has been made much more clear through watching his videos and being lucky enough to chat with him on the phone. This guy goes DEEP into what is possible with sound.
Hopefully this has cleared a few things up for you, now go make some music!
Jason
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