Wednesday, August 12, 2009

Give Ring Modulation a Try!

For as different as they can sound from one another, most analog synths are remarkably similar in terms of their architecture. You generally have an oscillator or two, that's fed to a filter, which is usually modulated by an envelope or LFO, which is then fed to an amplitude envelope to determine the final volume contour of the sound. It's pretty amazing the wide range of sounds you can get out of such a basic structure. But even with different oscillator waveforms and different filter types, there is a limit to what kinds of sounds you can get out of it. For example, this basic structure wouldn't generally be very good for making metallic or digital-sounding timbres. Add a ring modulator into the equation, though, and suddenly you can get some very atypical sounds out of analog synths (or softsynths).

Whether you realize it or not, you've probably heard ring modulation in action. The famous voice of the Daleks on the original Dr.Who are the result of ring modulation, as are some of the robotic voices in Star Wars. Ring modulation basically takes two sound sources (usually oscillators) and multiplies their frequencies. This process results in a sound that is made up of the sum and difference of frequencies in the two sources. These new frequencies, known as 'side bands', can create all manner of inharmonic sounds from sci-fi sweeps to metallic percussion sounds to harsh, atonal textures. Harmonic sounds are possible too with proper tuning of the two oscillators (or other source) against each other. If you want to make a bell sound on an analog synth, ring modulation is a good place to start.

In addition to synths featuring ring modulation, there are standalone ring mod guitar pedals and ring mod plug-ins for your DAW. These usually work by using your audio input as one of the 'oscillators' and multiplying that with an oscillator waveform (often a sine wave) that can have its pitch modulated. So with that explanation out of the way, here are a few things to try...

• The sidebands created by ring modulation will vary depending on how the two oscillators are tuned against one another. So your first port of call for experimentation should be to mess around with altering the frequencies of both oscillators. An amazing amount of variation is possible here. Most of what you hear will sound pretty dissonant and inharmonic, but you will also notice that a few certain intervals, the sound comes in 'tune' and takes on a bellish quality.
Try tweaking settings until you get something vaguely metallic . Set your amplitude envelope to an instant attack, short decay, and zero sustain and you have a starting point to thousands of synthy metallic percussion sounds.

• Detuning oscillators against one another is just a start, though. Where things get really interesting is when you introduce modulation so you can alter those frequencies in real time. Try setting up an LFO or envelope (or a step sequencer!) to modulate the pitch of one (or both!) oscillators and those static timbres suddenly spring to life.

• Even if you have no intention of ever using it in a song, do try feeding vocals, guitar, or any other 'real' instrument through a ring modulator to experiment. A lot of the results are very lofi and retro sounding (which can be cool on its own), but there are a lot of really interesting modern sounds waiting to be found in there, too.

Here are a couple quick examples, mostly from Gmedia's Oddity. The last example is a bongo loop being fed through Logic's built-in Ringshifter effect.


manson baptiste said...

thanks for this article !
I found ring mod really interesting to get some spectacular drops down in electronica. But I really like it for percussions:
Try playing with a short envelop on the transients modulating the ring mod volume, applied on harmonic, rich wave forms and you can get expressive percussions. I usually "flush" the bass content with a high pass filter and focus the harmonic content with a bandpass filter mounted in serie with a pretty low Q value to focus the harmonic content on one note.

A bit of white noise mixed with it can soften the harsh and electric results, getting some warmth back in the sound.

On the virus TI factory lib, there is a couple of patches that wisely use ring mod to obtain snares and toms.

As you said, it is difficult to obtain pure and harmonic sounds, but for FX and original percussions it is really efficient.

Anu said...

Making sure there's a difference between the oscillators is key, otherwise you just get NOTHING down low (no difference) and something an octave higher (freq + freq = 2xfreq).

SMALL frequency differences may result in a lot of low-end garbage depending on your synth architecture (440 Hz - 430 Hz = 10 Hz!). This could be bad for your setup.

Note also that some ring mods are based on fixed frequencies, which means the character changes across the keyboard.

If your synth lets you ring mod oscillators with key tracking, it can produce good timbral effects.

You can also use an envelope to apply ring mod just on the attack portion of sounds for interesting character - attacks matter a lot!

Tom said...

Great tips, guys!

Jack Astro said...

I made this a few years ago when I first got a Blue Ringer.