Here we look at how modulation can be used to massively expand the sonic pallet available when designing sounds. To help us with this we will be using Native Instruments MASSIVE synthesiser, a very powerful and versatile synth with a plethora of modulation possibilities.
Modulation
So far we have looked at the three main sections of an analog synth: OSCILLATOR - FILTER - AMPLIFIER. Using just these three building blocks - oscillator, filter and envelope generator - it's possible to create a huge range of sounds, both natural sounding and artificial. But a synthesizer can do much more than that. Most synths also contain other blocks or modules (i.e. LFO, envelope generator) that allows us to shape sounds in many different ways.
Moving a filter in real time creates interesting sounds, and this really is where analog synthesis becomes interesting, and allows to create original and unique sounds.
The very basic idea is that any of the three main modules (osc, filter, amp) can be ‘modulated' using other modules or parameters. An envelope generator, for example, is normally used to shape the volume of a sound - see the post on envelopes and ADSR. Here we discuss how that same envelope generator can also ‘modulate' other parameters, such as filter or pitch.
Let's take a look at this diagram and see how some of these modules or ‘blocks' can be connected in order to apply modulation.
As you can see in the diagram above, the LFO and envelope generator 2 can be connected to the oscillator, filter or amplifier, to create more interesting sounds.
How does it work?
The basic concept of ‘modulating' a sound, involves three elements:
- Modulation source: this is what will be used to make the changes happen. It can be actions from your MIDI keyboard, such as velocity, mod wheel, pitch bend, etc, or an envelope generator, LFO, or whichever other features the synth provides.
- Modulation destination: this is the part of the sound that you want to change. It usually is the volume, the filter and the oscillator pitch. But some devices like the ES2 can allow you to modulate many more parameters, and it actually refers to this as the Target
- Amount: It defines how much the source will affect the destination, the greater the amount, the greater the change.
Hardwired vs Modular
In many synths, the modules (blocks) are already connected (or hardwired, to use the correct terminology), which means you only have to fiddle with the modules parameters in order to create sounds.
In modular synths, they're not, which means they have to be connected using patch chords before you get any sound at all. Obviously, synths of the hardwired variety are generally easier to use, but modular synths are more flexible, since you can freely choose how to connect all these modules.
With the arrival of software synths, ‘hardwired' synths have become far more flexible, as you will find out using the ES1 and ES2 synths in Logic. In addition, some parameters can be modulated using certain functions of your MIDI keyboard, such as velocities, modulation wheel, etc....
As we have already discussed, not every synth offer the same features, some will have one or more oscillators, one or several envelopes, LFO(s), etc... But they will all follow the same basic connections we have mentioned before. What follows are some of the most useful techniques that will help you create better sounds for your productions.
Velocity Control
Setting how the Velocity controls Volume Most old analog synths were not velocity sensitive, nowadays all modern synths will respond to velocity. The most common use for that is to control the volume, so that basically the harder you press a key, the louder it sounds, and vice versa.
You have already noticed that most of the sounds you have used in the ES 1 already respond to velocity, but when you create a sound from scratch you will need to set it up.
Velocity response is set up using the vertical slider (as seen above) With the uppermost selector you can choose the loudest volume you want when you hit the keys the hardest (vel 127) and with the lowermost selector, the level you want the volume to be when you hit the keys the softest (vel 1) Setting how the Velocity controls the Filter Cutoff Frequency Velocity can often be used to control other parameters other than volume. You can also use velocity to control the Filter Cutoff Frequency for example.
Many real instruments will sound less bright if played at a low volume and become brighter when played loudly, so by applying velocity to both the volume and the filter will help you to emulate this effect. Here's how to set it up:
- Choose a Cutoff Frequency - something low is typical - say three notches up (that's about 140Hz)
- Adjust the lowermost selector to choose what frequency the cutoff will be when you play the keys the softest. This is relative to the Cutoff Frequency set so if your Cutoff is at the 3rd notch from the left and your lowest freq selector is at the bottom the Cutoff Frequency will be still the 3rd notch from the left. However, if you set the lowermost selector 2 notches up, the cutoff frequency will be increased by a notch when you play the keys the softest.Adjust the uppermost selector to choose the frequency cutoff value when you play keys the hardest. Higher values create a brighter tone.
- Adjust the uppermost selector to choose the frequency cutoff value when you play keys the hardest. Higher values create a brighter tone.
If you want to turn off velocity responsiveness click 0 in the middle.
Envelope Generators
As we have already mentioned earlier, the envelope generator output does not have to be applied to the amplifier section only. It can also be applied to other parts of the synth.
It is normal to allow the filter to be modulated by the main envelope generator (or to have a separate envelope generator dedicated to the filter). This allows you to make tonal changes to the note while it plays.
Some synths have only one envelope generator that controls the amp and filter simultaneously, but many devices have at least a second envelope generator that you can assign to the filter or sometimes other parameters.
A great example is the 'squelchy' bass sounds used for most electronic dance music. By having a zero attack, short decay and zero sustain level, on the filter envelope generator, you get a sound that starts with the filter wide open, and quickly sweeps down to fully closed. Add some resonance for a more dramatic sound.
An ADSR envelope shapes a sound in time. When used to modulate another part of the synth such as the filter for example, the envelope will work exactly the same way, but will affect the frequency cutoff instead of the volume.
Also note that some also allow you to apply an envelope to other section of the synth, such as the pitch of the Oscillator for example, as we will also demonstrate next. The ES 1 has a dedicated Mod Envelope for this job, and with the ES 2 you can use whichever envelope you want!
You might also want to try other possibilities, like applying the Mod Envelope to the pitch of the oscillator for example, so that when you press a note, the sound will go up and down in pitch according to the shape of the envelope. Great for sound FXs.
The Mod Envelope and routing matrix (set to Pitch) LFO When you apply periodic changes to the pitch of a sustaining sound, you obtain what is known as a vibrato. If the periodic changes affect the loudness of the sound instead, it is called a tremolo. Vibrato and tremolo are often an important part of the sound of acoustic instruments. For instance, a sustained violin sound without vibrato will sound surprisingly raw and unmusical.
Most synthesizers can simulate these effects by applying a slight, periodic change to the pitch of the oscillator (vibrato) or the amplifier (tremolo). Vibrato and tremolo effects require a rather slow wave that will modulate either the pitch or the volume of a sound. To create this modulation wave, synths use a module called LFO.
LFO
stands for ‘Low Frequency Oscillator'. As its name suggests, it's an oscillator that vibrates at a frequency way below our range of hearing. The LFO is not used to generate a signal that you can hear, but is used to modulate the other sections of the synth, to generate effects.
The LFO produces an output frequency, as does the oscillator. However, while the Osc produces an audible frequency (from, say, 20 Hz up to 20 Kilohertz), the LFO produces a signal with a relatively low frequency, it may range from 1Hz to 10Hz.
The two main parameters to control LFOs are:
- Waveform: Because a LFO is primarily an oscillator, it is not really a surprise that it generally uses the same waveforms as found in the oscillator section; such as sine, triangle, sawtooth, pulse, and random. Some devices offer other possibilities.
- Rate: Speed of the LFO defines how fast is the cycle of the waveform. Most new hardware or plug-ins synths also have a sync button so you can sync the effect to the tempo of the project loaded to rhythmical values such as 1/8, 1/16, etc.
Using a sine wave, for example, the pitch will rise and fall regularly up and down. With a frequency setting of around seven cycles per second, the result will be a musical vibrato. Crank the depth up, however, and it will turn into a siren! If a square wave is used instead of a sine wave, the pitch will oscillate between two pitches, rather like a trill. Select a noise waveform and pitches will be generated at random.
We have already discussed how some synths are completely modular, where you can select any modulation source (envelope, LFO, etc.) to modify any parameters (osc pitch filter cutoff, etc...). But not all synths offer this flexibility, and sometimes a modulation source will be automatically assigned to only one parameter. With that type of synth, LFOs are most often applied to the oscillator to modulate the pitch.
However many synths have the option to assign the LFO to many parameters.
The most common use is to assign the LFO to the volume envelope, to create a tremolo effect or to the filter, so the filter opens up and closes down following the LFO settings, when pushed to extreme, you get that bubbly effect, almost helicopter like...
How To Control The LFO
Ok, LFOs offer great modulation effects, but quite often we will want to be able to control when it starts affecting the sound.
Natural vibrato and tremolo effects tend to increase in strength as a note is sustained. For example, a flute sound might have a tremolo effect, which begins at some point after the note has sounded, and the tremolo effect gradually increases to a maximum level, where it remains until the note stops sounding.
There are several techniques you can use to produce this effect, often depending on the features of the synth you use. In the ES1 you can control the depth of the LFO (to make life easier you can think of depth as strength of the 'wobble') Not all synthesizers allow this kind of precise control over the LFO, and quite often we can only set a delay time before the modulation begins.
Another characteristic about both these methods, is that even though they allow to offset the start of the LFO, so that it gradually builds up in time, once the LFO is ON, it's there all the time, which might be what you want for some sounds, but sometimes you might want to have a bit more control over when the LFO is heard.
In many synths, the amount of LFO can often be controlled by different parameters, for instance in the ES 1, you can control how much LFO will be applied using the Router A common method is to control the amount of LFO using the Mod Wheel of your MIDI keyboard, so that you can change the amount of LFO applied in real time, which gives you far more control.
Furthermore, with midi synths & plug-ins, you can record theses changes in your sequencer on a MIDI track and edit them.
Portamento
Portamento
from the Italian word for travel, this is when a note rises or falls from one pitch to another. Portamento is often labelled ‘Glide' in many devices (ES 1 & 2 included).
The effect of portamento is a continuous "slide" up or down from one note to another, rather than a sudden change from one note to the next. This is most commonly encountered on string instruments, when a guitar, bass or string player slides on the neck of the instruments from one note to another for example. Trombone player can also create a portamento effect, using the slide on the instruments.
Many synths feature a portamento or glide function to emulate this effect. The portamento effect is a great function to add expression to a musical phrase, especially with monophonic lines, such as bass lines and lead type synths.
You'll find a controller that adjusts the time it takes for the notes to bend. Lower positions are faster whilst higher positions are slower.
Legato is a mode that is great for synth solos or basslines. To enable it, roll the mouse up over the 'Voices' section. When this is on, the Envelope is not re-triggered from the beginning if you already have a key held down - the pitch just moves up or down. A good example of this is that if you have your filter envelope set with a low sustain level and a decay of about half a second you can have a bright attack on the first note and then if the original key is still held down and you play another the new note will be warmer in tone. This allows for a more expressive performance and is the classic 'old school' analog synth mode.