Why is it called subtractive synthesis

When we hear the sum of those frequencies, we perceive them as a sound. This is true for non-musical sounds e. So, frequencies, their relative amplitudes, and how the relative amplitudes change over time all contribute to the timbre of the sound. The overtones of a piano playing middle C are different from the overtones of a violin playing the same note.

Additive synthesis works the same way to build sounds from the ground up. You add frequencies together at different amplitudes to define the overall timbre, or tone, of the synthesizer. These kind of synths have oscillators which usually only use a sine wave. You can build your sound up one harmonic at a time, which means with more oscillators, the more unique and detailed your final sound will be.

So when I say that the middle C on the piano is producing a frequency of Hz, I mean that the piano string or rather, wire is vibrating at a rate of times per second. Anything that vibrates at this frequency will give you the sound you hear at the piano when you play middle C. However, no sound produced in nature or on real instruments is going to give you such a clean harmonic tone. If that were the case, all C notes, whether sung by a man, woman, child, or played on guitar, piano, or ukelele, would sound exactly the same.

Yet, we can usually tell when a man is mumbling a C note, or if that note is being played on the piano. The dominating frequency is what we perceive as a note, sung or played.

On the other hand, if there is no dominating frequency, it is simply a noise. I want you to think of traffic for a second. How does it make you feel? But keep with me for a second…. How does traffic usually sound?

Sometimes loud and chaotic, sometimes just lots of wush-wushing sounds of tire, asphalt, horns, and engine revs. Now, I want you to think of the sounds of traffic as simply a bunch of frequencies producing the sound we call traffic.

Any sound in the world, then, that is produced naturally via an instrument will produce a traffic of frequencies. When there is a dominant frequency in the bunch leading the rest of the frequencies along the way, we no longer have so much noise, we have a discernible note. Back to our traffic example. What if, you just wanted to get the sound of a certain horn you hear? Are you getting the point yet? That is the basis of subtractive synthesis. Take a look at the video below.

The synthesist applies a band-pass filter to let through only a narrow range of frequencies. Now, enough about traffic and noise and stuff. You want to make music. Keep reading…. In order for you to first subtract, you need to add something in the first place.

What a subtractive synthesizer does, initially, is to create a raw sound using one or more oscillators devices that create vibrations to produce sounds, like the vibration of a piano wire. In other words, think of it like sculpting. A sculptor takes a raw boulder and chips away bits of it until you get the sonic equivalent of the Statue of David.

But we will get to these shortly. The reason why we are using a square wave instead of a sine wave is that square waves, due to their shape, produces a fairly harmonically rich tone. Sine waves, on the other hand, produce pure sounding tones. They have half as many harmonic frequencies as a Sawtooth does, which repeat every second cycle.

Square waves are a particular type of pulse-wave. As the name suggests, the signal pulses on and off. Pulse waves are commonly used for pulse-width modulation PWM , which was used in early synthesizers to replicate two oscillators interacting with each other. This means that they are good for creating wind instruments, like a clarinet. Similar to a Square wave, they contain the odd harmonics of the original frequency. However, the volume of these harmonics drops much more quickly.

People hear changes in frequency as changes in pitch, i. In a synthesizer, the fundamental pitch of an oscillator is often controlled by either a Tune knob, or broken into steps that are labeled in feet, i. This idea of measuring pitches in feet comes from old pipe organs, where the pipes were arranged in different lengths for different pitches.

Many synths have more than one oscillator. By building individual layers and combining them, you can create some truly huge sounds! The Low Pass Filter allows the low frequencies to pass through, cutting off the high frequencies and creating bass sounds. The High Pass Filter does the opposite. A filter does not just stop the sound abruptly, it slopes down from the original volume.

The Slope is measured in decibels dB per octave, which is why you might see a dB or dB filter on a synthesizer. The higher the number, the steeper the slope and the stronger the filter. Most filters have a Resonance or Q control. Patch sheets So, you own an old monophonic analogue subtractive synth and you need to record your sound setups.

Also known as "Analogue Synthesis", subtractive synthesis was the original synthesis method developed for the early synthesisers of the 's and 70's. Subtractive synthesis produces distinctly synthetic sounds and involves using Oscillators to create changing electrical pressure soundwaves which are then processed, or "Modified" to alter their pitch, frequency content and amplitude over time. In essence, elements of the original waveform are "wobbled" and "subtracted".

The classic subtractive synth, the Moog Minimoog. Architecture of a simple subtractive synth. Oscillator controls on NI's Massive software synth. Prophet 5 LFO controls. Filter cutoff control.

Filter controls on NI's Massive software synth. Filter resonance.