Synth properties

All synthesizers share a number of common properties that are outside of mechanics. These terms purely relate to the signal that these synths create in their output. When we create or tailor these properties in some method, we are practicing a concept known as synth design.

## Basics of Sound

The earth has squashed enough air around us that whenever the air happens to move, it slaps our ear drums. Our detection of these rapid vibrations in the air, often caused by a predator's growl, a bunch of shaken leaves, or the speakers emitting your synth, is the physical definition of our perception of sound. Our ears can pick up these vibrations through the air (via the drum), or they can pick it up through our jaw bone if a part of our ear detects vibrations to it (meaning that losing your hearing may not doom us to total deafness). If you lose connection between the ear parts and the brain, however, game over, so don't do that.

Synths are often made with sound generators that function according to a pattern described as an oscillation. Speakers will use the act of compressing air and decompressing air to generate the air movements that result in the slapping of our ear drum. If you look at the diagram above, you'll note some of the basics of how we visualize sound, such as the fact that a straight line dead in the center from left to right represents perfect silence.

## Basic Audio Terminology

* A **cycle** is the unit of vibrations.
* The speed of vibrations, or the number of vibrations within a time period, is the **frequency**.
* The standard frequency units are in **Hertz**, and are measured in cycles per one second.
* **KHz**, or **Kilohertz**, is 1000 Hertz.
* The **Audible Frequency Range** is the physical limitations to which we can hear sound. We cannot discern above 20KHz.

If you control the vibrations, you control the synth design.

## Basic Properties of Synthesizers

* **Volume** is the amount, or amplitude, of the audio signal being generated.
* **Frequency** is a term for the rate of peaks a sound makes across a unit of time. In sound, we analyze the same sound in multiple frequencies and track the loudness the sound makes in each frequency. This is called a spectrum and we use a spectrogram to view it.
	+ **Pitch** is the perceived frequency, or musical note (including off-key), the audio signal makes. For example, any instrument (guitar, synth, snare, etc) that emits 440Hz will universally be perceived as the A note above Middle C.
	+ Many sounds are comprised of various combinations of frequencies. We first have our fundamental frequency, which is what the note being played should be, and on top we have additional frequencies that contribute to the timbre and spectrum (the tone) of the instrument. These additional frequencies are known as **harmonics** (also known as **overtones** or **partials**).
* **Timbre** is an umbrella term for the different audio properties a sound is comprised of. When two sources of audio play the same note, the differences in sound that they make, despite being the same pitch, is their timbre. Some of the specifics of said differences can include things like their harmonics, envelopes and spectrum.
* **Envelope** is a term for the curvy path that is made out of the extremes of an audio wave. Thus there is an upper envelope and a lower envelope. Consider how vibrato is a wavering loudness (singers and physical instruments will wiggle their pitch to help achieve this). You'll see a very active and winding set of envelopes, as a result of that. All synths will, for example, have some form of volume envelope.
* **Spectrum** is a term for a sound's arrangement of frequencies (including harmonics) across time. Often you'll hear of tips involving the use of equalization, which is where you take the noise and (usually) subtract certain frequencies before the sound goes to the speaker. Most sounds will have loudness in multiple frequencies at any given moment.
* **Brightness**/**Darkness** is a shorthand way of describing the timbre of a sound with relation to harmonics. Bright sounds will have higher harmonics while darker sounds will have lower harmonics. Filters can help fluctuate a sound's "luminosity" to dynamically affect the spectrum of the song, one case being classic dubstep.

One application of these concepts is to create a bell instrument. By taking a harsh sawtooth noise, adding a volume envelope that involves a fast attack and slow release, and then intentionally introducing dissonant harmonics on top of the fundamental, what happens is that we create this ringing synth that contains a metallic tone made possible by intentionally making the harmonics metallic. You'll notice in the next page that this is an example of following subtractive synth design.

## Common Synthesizer Components

This wiki will go into the subjects for each component of synthesizers in the "Next" link at the bottom of the page. Synthesizers, despite their many algorithms and features, will commonly have the following components:

* **Oscillator** for generating the sound.
* **Amplifier** for adjusting volume.
* **Filter** for reshaping the volume in subtractive design.
* **Volume Envelope** for shaping the synth's volume over time.
* **Filter Envelope** for shaping the synth's filter over time.
* **Pitch Envelope** for shaping the synth's pitch over time (this became less common, recently).
* **LFO (low frequency oscillator)** for automatically adjusting values (such as volume) over time.

Topic: Basics