By: Saverio

What's a synthetizer, how it works and can be used

In my first post i decided to talk about synthetizers, the instrument i like the most (i'm a keyboard player...what's strange in that? :) ).

The reason why these machines exist is to synthetize sounds, the synthetizer (AKA synth) was born in the beginning of the last century, one of the first examples is the Theremin (create by the russian Lev Theremin in the first years of the 900), this instrument is played without touching it, just moving the hands around its antennae changing this way a magnetic field that modulates the sound of its oscillator.

The main compontent of a synth is infact the oscillator (othe oscillators in modern synths), this oscillator can create different waveshapes according to the synth tecnology used, in the most common (subtractive synthesis), the oscillator makes harmonic rich waves (such as the square wave, or the saw wave) from wich harmonics are subtracted using filters.

The base scheme of a subtractive synth is then made of two elements, an oscillator and a filter.
This kind of synthesis is today the most common and make possibile to have full and fat sounds, but often is flat and boring since is missing time variation of varius paramters of the sound (tune, amplitude, etc.) that are typical of "real" instruments, for this reason to these two base blocks we add other elements that are used to modulate the sound in the time domain, they are mainly two devices:

• LFO - Low Frequency Oscillator
• Envelope Generator

An LFO is similar to the main oscillator, with the only difference being the range of frequency (it usually works inthe subsonic range, 1-20Hz) and it's usually used to create modulations on the signal, for example it can be used to create a "tremolo" effect when you modulate the amplitude, and a "vibrato" effect when you modulate  the pitch.

An envelope generator enable you to recreate the volume variations of the real instrument. If you press a piano key for example, the sound will be stronger at the beginning then it will start to decrease as it progresses, an evelope generatore allow to reproduce a similar effect.

The simpler envelope model is the AR (Attack - Release), with two parameter we can set the time that it takes to the sound to reach its maximum volume and the time it takes to decrease and fade out after the key has been released.
Modern synths use more complex envelopes, the most commmon is the ADSR (Attack - Decay - Sustain - Release), the first parameter set the attack time of the sound, the second the decay time, the third the level to which set the sound volume for the lenght of the note, the last the cay time after the key release.

Both the LFO and the envelope generator can be (and ARE!) used to modulate different parameters and not simply pitch and amplitude, for example we could use an envelope on the cutoff frequency of a filter to change its frequency response with the time to create a brightr sound at the beginning and a darker one at the end, or we could use an LFO on the same parameter to create a wah wah effect.

Modern synth offer a lot of modulation options to create complex and different sounds, the most complex ones have unlimited stage envelopes for example, so tou can really use you creativity do "forge" new sounds never heard vbefore, there are a lot of free virtual synth on the internet, have a look to KVR!