Rockové klávesy - Analogová syntéza zvuku od základu – část 1.

Analog Synthesis In-Depth - Pt 1

Welcome readers! This month, we will begin a three part mini series on analog synthesis. Analog synthesizers like the Minimoog, Arp 2600, and Prophet 5 revolutionized the music of the 1970’s as well as being widely used in all genres of music today. Artists like Stevie Wonder, Yes, Emerson Lake and Palmer, and Herbie Hancock pushed these instruments to the limit of their abilities creating amazing sonic masterpieces in the process. This month, we will focus on the origins of analog synthesis and give an overview on how these interesting electronic devices turn electricity into sound.

Early Analog Synthesizers

The first analog synths actually appeared in the 1920’s and used vacuum tubes and newly developing electro-mechanical technology. One of these early instruments was the Ondes Martenot invented by Maurice Martenot. This instrument was used by French composer, Olivier Messiaen, most notably in the piece Fête des Belles Eaux. Another early electronic instrument invented in 1928 was the Theremin which makes an appearance in the Beach Boys hit Good Vibrations and in the Led Zeppelin’s rock anthem No Quarter. Although not usually thought of as an analog instrument, the Hammond Organ, invented by Laurens Hammond in 1935, used magnets and spinning sine wave generators called tone wheels manipulated by drawbars to create its magical sound.

Late 1960’s Analog Synths

In the mid to late 1960’s modular synthesizers appeared on the scene. These instruments made use of patch cables to connect different components such as voltage controlled oscillators, filters, and amplifiers. The downside of these first modular synths was that most were very expensive and often had hard to find glitches in the units because the patch cables would break. As an answer to these problems, Robert Moog designed the smaller, cheaper, pre patched Minimoog in 1970 that had all these connections hardwired in the unit. The Minimoog influenced the design of nearly all subsequent analog synthesizers, with a keyboard, pitch wheel and modulation wheels. It also included a three part signal chain consisting of an oscillator, filter, and amplifier that has become standard on almost all analog keyboards. Let's take a look at this three stage process of sound creation.

1) Pitch created by an oscillator

The beginning of this chain starts with an oscillator. An oscillator, quite simply, is a device for creating waveforms. On older analog synths these have names like square, saw tooth, and triangle which we will investigate more later in the article. For now, let’s just say an oscillator is a circuit that produces a periodic electronic signal by converting direct current into a alternating current signal. These different waveforms have different sounds depending on the "shape" of the signal produced. The difference of the harmonic content of these waves can be seen on an oscilloscope.

2) Tone (timbre) shaped by a filter

It wouldn’t be very interesting if we just had pure waves for our synth sounds. This is where the filter comes in. There are a few different types of filters which we will focus on next month. For now, let’s say the most common types are hi pass, low pass, and band pass. These different types of filters effect the waves mostly by two main controls; cutoff frequency and resonance. The cutoff frequency determines the point at which the filter starts filtering and the resonance amplifies the frequencies around the cutoff point.

3) Loudness controlled by an envelope generator

After the filter, the sound travels to a volume envelope which, on most synths, has four parts. By manipulating these four variables, the way the sound behaves after a key has been stuck can have great variance:

Attack: The length of time it takes a sound to reach it’s full volume.

Decay: The time it takes for the volume to reach the second volume level known as sustain.

Sustain: The volume level at which the sound sustains after the decay phase.

Release: The time it takes for the volume to go to zero. When this setting is higher, the sound will continue even after the key is released.

Different Waveforms

www.youtube.com/watch?v=nLKiGwdMgig

Waveforms all have different tonal characteristics. The addition of harmonics is what causes each to sound differently. Let’s take a look at a few of these common waveforms. Please check out the video link to hear the differences. I've also enclosed an image so you can see the different shapes of each wave.

Sine wave: The sine wave produces a very simple flute like tone with no harmonics.

Triangle wave: Somewhat similar to a sine wave but contains a few harmonics.

Square wave: Is made up of an odd number of harmonics and has a “hollow” sound. The more odd harmonics are added the more “square” the wave becomes.

Saw tooth wave: Contains all harmonics and sounds sharp and brassy.

Noise wave: Has a combination of many frequencies and harmonics and sounds like... well... noise... quite frankly. -:)

Tune in to part 2 of Analog Synthesis next month where we will begin to investigate how filters are used to color the raw waveforms.