Basics of Synthesis - A.Armstrong

Basics of Synthesis

All audible waves have wavelength frequency and amplitude. Wavelength is the measurement between the same point on one full cycle of a wave.



Frequency is the proximity each wave has to each other over one full cycle; it is the length of their wavelength. A frequency with a higher pitch will show waves very close and packed together (short wavelength) whereas waves that are far apart (long wavelength) have a low frequency.

Amplitude is the height of the wave from its middle point (0 on Y axis) to its peak. This shows the volume of the sound. The higher the peak of the wave the louder it will be, the shorter it is, the quieter it will be.

All sounds start with waves. In terms of music synthesis these waves are produce using an oscillator, the most basic and simple wave being a sine wave. A sine wave in constructed with one harmonic, known as the fundamental harmonic. For example, this could start with a pure A note at 110Hz, which could then have another wave at 220Hz added, and then another at 330Hz, and 440Hz. This would then be known as multiples of the fundamental (or integers), because it has been increased by an octave each time (double), so the tones still resonate with each other but it has created a more complex sound. Over tones can now be heard and this develops into a "saw wave". It is created by adding each harmonic consecutively, so, 1, 2, 3 etc.

Using this method other waves can be created, for example, by adding every other harmonic, 1, 3, 5, will create a square wave. Rectangle waves are like square waves but less symmetrical. Their duty cycle is usually at 25% or 75%, meaning there will be a shorter first cycle of the wave, or a longer one. They are also known as 'pulse waves'.






Certain instruments produce different waves

For example, I have used an ES2 synthesiser to create on of my samples, and started by using the 3 oscillators to combine waves. In the first oscillator I selected a sine wave and put the dial on frequency modulation. This works by varying the instantaneous frequency of the signal, in other words the frequency will modulate between short and long wavelengths periodically. The second oscillator is placed on a sawtooth wave, that is synced with oscillator number 1. The third oscillator has a square waved selected, with no modulation to a rectangle wave. This mix of waves allowed me to create a slightly zesty but muffled sound, with a very warm feeling to it.
I noticed that using a synced saw wave made my sound more bass-y and fulfilling, and this was emphasised when I change the frequency dial to -12, this means whenever I play the note anywhere on a keyboard it will sound lower in general. In relation to ADSR, my sample has a fairly short attack, with a slight delay. The sustain is set on high as well as the release and decay, so its rings out for a long time with or without a key being pressed. Attack, decay and release are all time measured parameters, while sustain is a level. Envelope 3 is is the ADSR affecting the sample, envelopes are used to control the value the parameter, they can be used to make a sound more natural, and adjust the levels of a real life instrument.
LFO's (low frequency oscillator) are not a type of sound but are used to control the parameters of sounds that are created with a synth. They will function around 20Hz and are commonly used to create tremolo effects on synth basses, or that classic 'wub wub' sound heard in dupstep. Here is an example of where I've used it in my own work. (insert link) .    ES2 Sample

For the most part my samples have been made using subtractive synthesis, because I have built up on top of waves and used filters, envelopes and LFO's etc to adjust the sound.

Cakewalk Z3TA2

The Z3TA2 has 6 wave table oscillators, compared to the ES2 which only has 3 oscillators, that allow for a wider range of adjustments to the waves making them more complex than just the classic analogue waves like saw and square. It has the ability to also make detailed changes to the waveform with 16 waveshape sliders, making samples sound extremely unique, the ES2 only allows you to blend 3 waves together with a triangular mix field.  The ES2 and Z3TA2 both have 2 filters that can operate in series or parallel but the Z3TA2 has 9 variations on low/band/high pass, band reject and formant filter. It also has 3 resonant modes and a comb filter. This makes gives the filtering of sounds created more depth. ES2 has 2 LFOs but the Z3TA has 6, that also allow you to control fade in offset and delay. There is also a strong visual aspect of the Z3TA2 that is not present in the ES2, because you can see the exact shape of your waves, filters, LFOs and ADSR through a graph representation 

Synth patches and sample patches

1. ESE synth - for this synth I chose a rectangle wave from the oscillator that had 3 variable waves, square and rectangle, that allowed me to set the space between each wave form, and sawtooth. I set the cutoff at about 35% and the resonance is quite low so it takes of the high end making the sound more bass focused. The speed dial is set high, which effects the rate of the tremolo on the sound. The attack is set fairly low so theres only a slight delay before reaching its maximum. It is basically an instant strike. The release is slightly higher and will last a short moment after the key has been released.

2. ES2 synth -