Introduction to synthesizers
November 8, 2009
Evening all,
Over the past few weeks I’ve researched into the basics of FL Studio and am ready to start making my track. Before I do, there is still another thing to talk about. Trance (and many other genres of music) wouldn’t be possible without the synthesizer. We will want to use a synth to create sounds so it’s best to learn the basics now.
I want to get to the level where I can hear a trance tune and know how to reproduce that sound in a synth. That will take time and practise. What I’ll do this week is go through the fundamentals that I’ve been learning about so we’re all on the same wavelength. I’ve read a few things on the Internet and have also purchased a magazine called ‘Computer Music Special 38 – Make Synth Music’. Do a Google search and you will find this (or get in touch with me and I can point you in the right direction). This mag goes through all the basics, gives you a CD with tutorials and gets you creating sound patches, pretty cool.
There are so many synth plugins out there, including free ones. Although they all have their own unique touch to them, they tend to have a similar set of features. There are also different types of synthesizers and synthesis methods (such as additive, subtractive, fm synthesis). What I want to do here is choose a freeware subtractive synthesizer and see how it works. Most of the information will be outlined below. However, to hear examples of how the settings affect the sound, play the video on the right where I go through the controls and play notes.
Subtractive synthesis
A synthesizer is an instrument that can generate sounds. Subtractive synthesis means that you start with some waveforms that make sound, then you keep taking chunks out of it to finish with the sound you want to be left with, i.e. you’re subtracting bits out of it. Think of it like sculpting an object out of a block of ice, you chisel it down to create the object you want.
I will use a synth called ‘TAL-Elek7ro’ which you can download from kvraudio.com for free. Here it is.
Synths initially look scary but when you learn to identify the common characteristics that exist in most synths, they aren’t as scary. Let’s take a look at the important parts of the synth in the order they are used to create the final sounds.
Oscillators
It all starts here. The oscillators are what generate the initial waveforms that produce sound. Different waveforms have a different sound and the common types are: sawtooth, square, sine, triangle, noise. Each has its own characteristics and if you do more Google research, you’ll learn about these characteristics and harmonics.
Most synths allow you to change the shape of the square waveform with something called ‘pulse width’. It’s just changing the shape so the high points and low points aren’t the same width. This changes the sound.
There is also a way to change pitch of an oscillator by detuning them. Usually you’d be using 2, 3 or more oscillators to generate a sound and detune them slightly to make the sound interesting (something we’ll do in the video).
Mixer
Once we have a few oscillators generating sounds, we can use the mixer to decide the volume level of each oscillator in the mix and the overall volume level. More advanced synths will also have ways to manipulate an oscillator’s pitch with the output of another oscillator. This is called FM Synthesis (frequency modulation).
Filter
Now that we have our waveforms creating sounds, we want to filter out the frequencies we don’t want (recall the sculpting analogy). The main parts of the filter will be the cutoff frequency and resonance. For those of you that follow my vids on www.mixingguide.com, you’ll recognize these settings on a DJ mixer.
There are different types of filters. LPF (lowpass filter) is where all frequencies below the cutoff get through and anything above is removed. It’s like keeping the bass sounds and removing the high-pitched sounds. HPF (hipass filter) is the opposite, so all frequencies above the cutoff get through and the bass is removed. BPF (bandpass filter) remove everything above and below the cutoff, just leaving the frequencies around the cutoff to remain.
Resonance is a way to boost the frequencies around the cutoff and feed it back into the signal, creating interesting sounds.
Sometimes you’ll also see a filter slope setting, commonly 12db or 24db. This just determines how precise the filter is, 24db being more precise than 12db.
Envelopes
Synths aren’t that exciting unless we can manipulate the sound to change over time (even a very short space of time). This is what is referred to as modulation, i.e. modifying the sound. There are a few ways to do this. Let’s start off with envelope generators, commonly referred to as EG. Following is a diagram showing an ADSR envelope which is the most used.
As you can see there are 4 stages to the envelope. This determines how the sound changes over time. Note that envelopes can be applied to the filter or to the sound amplitude. The former will change the cutoff frequency over time and the latter will change the volume.
A (attack) – the length of time from hitting the note to reach up to full volume/frequency
D (decay) – the length of time after attack to go down to the ’sustain’ level of volume/frequency
S (sustain) – the volume/frequency level heard whilst the note is being played
R (release) – the time taken to reduce the volume/frequency to nothing once the note has been released
You’ll see in the video how these settings affect the sound.
LFO
Another modulation source is the low frequency oscillator (LFO). This is an oscillator that is played at such a low frequency that you can’t hear it. It is used to change another parameter of the synth over time. The parameters it can modulate depends on the options the synth gives you. Common parameters are: cutoff frequency, oscillator pitch, volume, pulse width, resonance, panning.
The idea is that you tell the LFO how much to modulate the parameter by, i.e. the intensity. You also tell it how fast to modulate, i.e. the rate/frequency.
The oscillator itself can have a waveform chosen by you so you determine the shape of the modulation. For example, if you wanted to modulate the volume with a triangle wave, the volume would go up to a peak then come back down gradually, then go up, then come back down, etc. A square wave would go up and down abruptly.
Another setting you may find in the LFO is for syncing. This is useful because if you have the VST plugin in your sequencer application, you can sync the oscillations to the tempo of your track. This would then override any custom rate setting and just use the host’s tempo, eliminating the need for you to guess what rate setting to use to make it sound good.
You may also have a setting that tells the LFO to start the oscillation from the beginning of the waveform each time a new note is pressed. Without this, one note may start at the beginning of the waveform (e.g. in our volume example, at low volume) and another note may start in the middle (high volume), therefore sounding inconsistent.
Effects
Although your host application can be used to add effects to the sound, some synths also have the ability to add effects before the sound gets to your host application (in my case FL Studio). This can reduce the overall CPU usage so may be worth considering. The effects offered will be different per synth and may include chorus, reverb, delay, echo and more.
Until next time….
Well, a short introduction it may be but it’s a good start to synths. That will do for now. It is a huge topic and there are a lot more resources out there on the topic. If I’ve mentioned something here that you don’t agree with or need more clarification on something, feel free to mention it in the forums.
Now we are in a position to start making our track and that is the focus of the next post. Let’s do this.
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