Let’s Play #12 – Adding Expression To Your Sounds
by Jerry Kovarsky
There are times when we want to interact with a sound and add some expressive variation to the phrases we are playing. While this is usually done on single note melodies, that is not the only scenario. My assumption for this discussion is that you want to be able to be in control of these moments in real-time. Let’s explore how that can be done.
All sounds can be evaluated by three main characteristics: pitch, timbre and volume. Pitch is controlled at the oscillator level, with the tuning parameters. Timbre is a multi-faceted characteristic, and is defined by things like the waveform/wavetable choice, filter characteristics, and forms of modulation and effects: think of adding distortion, or waveshaping, or a phaser/flanger etc. Volume is controlled by the Amplifier, and/or Mixer level.
Often, expression is already built into a sound by the use of an envelope generator routed to one of these parameters. A sound might have a slow fade-in created by the envelope shape routed to the amp, a filter may be swept open or closed by an envelope, and things of this nature. But you are not in control of these aspects in real-time. Let’s define the most common forms of expression as they relate to acoustic instruments, and see how they are created in synthesis techniques.
Vibrato is the most common form of expressive modulation in music/synthesis. An LFO is routed to the oscillator pitch, and often a Mod Wheel or joystick controls the amount of modulation. Using the Argon8M I have noted those routings in yellow:
With the wheel all the way back there is no vibrato, and as you move it forward you increase the amount. Because vibrato is a smooth modulation of pitch up and down, we usually use a sine or triangle waveform for the LFO.
The most common tweaks you might make to personalize this setup are to choose the rate for the LFO, and the amount of modulation introduced by the wheel/joystick. Take some time and listen to recordings of various acoustic instruments like solo string players (violin, cello etc.), and blues and rock electric guitar players. You’ll notice that there is a wide range of speeds that they perform their vibrato at, and they will often increase and decrease their vibrato amount while holding a note. Natural vibrato is emulated with an LFO rate around 6 Hz, but you are free to increase or decrease that to taste. In the following example, I start with a basic sound, and then introduce the vibrato gradually. I do this demonstrating three different LFO speeds: all sound good and natural to my ears.
In this next example I use a much faster LFO rate. While not as natural, it works well for short bursts at the end of notes.
A nice tweak to help make vibrato more expressive is to also increase the LFO rate slightly as you move the wheel/joystick forward. This is done by routing the wheel/joystick to the LFO rate (see red highlight), with a small amount of modulation used.
It is common for many wind instruments (including the human voice) to also slightly vary the volume of the note when producing vibrato. When the volume of a sound is smoothly varied to a large degree we called that effect tremolo. It sounds like this:
This effect is achieved by routing an LFO to the amplifier volume, or to a Mixer output in the synth. When we want to combine it with vibrato/pitch modulation we want much less of a tremolo effect. So route your Sine or Triangle LFO wave to Amp Output (on the Argon8 this is achieved using the AEG level – see red highlight), either using the same LFO you are using for pitch variation, or another that is set to the same rate. Have the depth of modulation less than your pitch modulation, or to taste. It’s a subtle effect, but can be very effective.
Another way to emulate varying the loudness of a note is to modulate the filter cutoff, so the sound gets a bit darker and then returns to normal. To achieve this, route your LFO to the Filter Cutoff using a negative amount (see red highlight).
That sounds like this:
There are lots of ways to introduce timbral change in realtime when playing. One of the most common is to play around with the Filter Cutoff in some fashion while playing a line. Of course you can reach out and turn a knob/move a slider assigned to the cutoff. Another is to route key velocity to the cutoff so your dynamic touch will vary the filter. And you might also tie that control in to the Filter Resonance while you’re at it. Just don’t modulate that too much, or you’ll hurt your ears/damage your speakers!
Here’s some lines played with velocity modulating the filter:
I like to find ways to add some grit and growl to notes as a form of expression. Sax players do this by adding what they call growl, or overblowing to their sound. Guitar players will dial up the amps or stomp on a pedal when they want more edge. This can be controlled by a dedicated knob/slider/ribbon/touch, and varied as you play to add variety. Or again, it can be tied into velocity so harder-played notes have more grit, and softer ones are more pure.
I sometimes like combining this type of timbral change with the LFO-based vibrato to make those gestures more interesting. Here’s an audio example with the Mod Wheel/Joystick introducing some Phase Modulation by itself, and then combined with a slight amount of vibrato. I dialed back the vibrato amount from what I would usually use, so the Phase Mod could stand out.
As mentioned earlier, tremolo is a common expressive gesture used by some wind instruments (think flute) in place of vibrato. So you should explore using it in your synthetic sounds, when you want to impart a sense of “acoustic but not anything I’ve ever heard”. Here again I’ve routed an LFO to Amp EG Depth (see red highlight). This is a good case for using the Mod Wheel/Joystick to modulate both the LFO depth and slightly increase the LFO speed (see yellow highlight) as well.
Many synth patches will use velocity to modulate amp level, making a sound dynamic to your touch. But any sustaining instrument (the human voice, organ, winds, brass, strings etc.) can increase and decrease the sound level while a note is being held. Giving yourself this type of dynamic control will really make your melodies “sing”. All you need to do is route the controller of your choice directly to something that will control the volume output your synth has, and then learn to play that controller as part of your performance. Common choices include the Mod Wheel, a pedal, a ribbon, or a slider if it has a long enough “throw” to feel comfortable. In this example I have set a slider on my controller to send MIDI CC#11 (Expression), and then I routed that to the AMP-EG Amount of the Argon8 (see red highlight).
My final tip is something that many synth programmers do to make sounds more expressive under your fingers without involving any other controllers. Set up a slow attack to a sound (see red highlight), and then route velocity to Amp EG start time with a negative modulation amount (see yellow highlight). When you play lightly the sound will have a soft/slow attack, but as you play harder the attack will speed up. Adjust this to your taste and touch. You can also do the same for the Amp EG Release, so softer playing is both slower and longer, and as you dig in more the sound tightens up.
Jerry Kovarsky is highly respected in the music industry. For more than 30 years, he worked as brand manager, product manager, marketing director, product developer, and product demonstrator for Korg, Ensoniq, and Casio. An accomplished keyboardist, synthesist, and author of Keyboard for Dummies, Jerry passionately advocates for making music with keyboards. After studying at the University of Miami and graduating from William Peterson College with a BA in Jazz Studies, an opportunity to demonstrate early portable keyboards sidetracked his professional aspirations. He likes living at the intersection of technology and art, balancing his time between writing, sound design, practicing and playing keyboards and his new granddaughter.