I recently made a video — “Total Stereo Immersion: Dual Behringer Pro-800 Synths for 3D Analog Soundscapes” — about creating deeply satisfying 3D stereo sounds and performances by using two of the same synthesizer modules, one panned hard left and one panned hard right. Each synth module was played by the same MIDI keyboard so that both sides were playing the exact same notes at nearly the exact same time. By changing a parameter knob on either synth, you could change the stereo perspective of just that parameter. By changing multiple knobs on either side, you could create an evolving, complex, stereo sound by giving each aspect of the sound a unique stereo perspective.
What I did not expect were so many user comments suggesting various ways to achieve a similar effect. While many of these suggestions certainly would create a stereo space, most won’t have the beautiful real-time playability and spatial complexity shown in the video.
This article will explore many of these different ways of achieving stereo for synthesizers and workstations, ending with a deeper description of the method I used in the video. I’m going to keep the technical talk to a minimum and focus more on each method’s sonic results.
Here are some of the many ways to achieve a spacious stereo sound with your synthesizers and workstations.
Stereo Chorus
Whether it’s built into your synth or a separate effects pedal (or rackmount unit), a chorus takes a delayed signal and modulates (wiggles) the delay time up and down. This makes the pitch of the original sound go up and down slightly. This is then combined with the dry signal (often 50% dry, 50% wet) to create the chorus sound. Stereo can be achieved in several ways; one common way is to have the pitch go slightly up on one side while the pitch on the other side goes down. The original, dry signal goes to both sides.
For my performances, I might use a stereo chorus pedal as it’s relatively inexpensive, easy to learn, and easy to tweak in real time. And, when you first hear these pedals, they sound amazing. However, keep in mind that this deliciously thick and wide sound is a singular repeating effect that is applied to the final audio signal. Over time, you’ll become aware of the speed and cyclic nature of the effect, which makes it more obvious that it’s something unrelated to the original audio. More importantly, if that chorused stereo signal ever gets summed to mono (via a mono PA, mono floor monitor, or additional mono effects), then you can get very strange phase artifacts caused by the two signals merging.
Stereo Phase Shifter
A phase shifter runs the audio through a special filter called an all-pass filter. It changes the phase of some frequencies while leaving others intact. When this is combined with the dry signal, it causes some frequencies to be boosted and other frequencies to be cut. Modulating this filter will cause the well-known phaser sweeping effect. Stereo can be achieved by sweeping one side’s all-pass filter frequency in one direction while sweeping the other side’s all-pass filter in the other direction.
Stereo phaser pedals are relatively inexpensive, easy to learn, and easy to tweak in real time. They can sound amazing for a while, but they use, again, a repeating effect that is applied to the final audio signal. Like the stereo chorus, you’ll become aware of the speed and cyclic nature of the effect, which makes it more obvious that it’s something unrelated to the original audio. Stereo phasing can also cause unwanted artifacts if the stereo signal is summed to monaural.
Ping-pong Delay with Modulation
A delay with a stereo ping-pong effect can deliver a stunning stereo ambience. It works by first playing your synth’s dry signal in real time. Then you’ll hear the first delay (let’s call it 200ms) on the left side. Another 200ms after that, you’ll hear the second delay on the right side. A feedback knob determines how long those repeats keep going before they fade out. By gently (and slowly) modulating those delay times, you’ll also get a stereo chorus effect on top of the ping-pong effect.
Stereo delay pedals (with ping-pong and modulation) are medium-priced pedals, not too hard to learn, and easy to tweak in real time. Because of the complexity of the ping-pong effect and the subtle motion of the modulation (especially if it’s very slow), the result sounds much more like an organic part of the original sound. Like the other effects, though, you may encounter problems when summing to mono. Also, you probably don’t want an echo effect in every song.
Panning via Key Tracking
Stereo key tracking is a parameter that pans notes to the left the farther down you play on the keyboard and pans them right the higher up you play on the keyboard. This was initially created to simulate the effect of an acoustic piano, but it can be applied to any sound. The beauty of this method is that it costs you nothing if it’s already a parameter on your synth. By using it differently on different sounds at the same time, you can get even more complex stereo images. Best of all, it’s usually not a problem if the stereo signal gets summed to monaural.
Alternate or Random Panning of Notes
Some synths allow you to pan every other note to one side or the other. They may even have the ability to set how far the alternate panning is from the center. There may also be an option to choose between alternating or random panning. This is a great trick to try as it opens the stereo field without any additional artifacts. Like key-track panning, it costs you nothing if it’s already a parameter on your synth. By using it differently on different sounds at the same time, you can get an even more complex stereo image, and it’s usually not a problem if the stereo signal gets summed to mono.
Duplicating and Panning Layers
You can create strong stereo fields with synths and workstations that have layers. After creating a layer that you like, you can duplicate the layer and pan one layer to the left and one to the right. By gently raising the pitch on one side and lowering it on the other side, you can create chorusing stereo images that seem larger and bolder than only a single layer. The main cost of this method is a reduction in your synth’s available polyphony since the “stereo” sounds will use two notes for every note you play. If you have enough polyphony, then go for it.
Multiple Takes in a DAW
Another way to create a powerful stereo image is to record both an audio track and a MIDI track of a synth performance in your DAW (digital audio workstation). Now, use the MIDI track to drive the same synthesizer on the same preset but with some slightly different parameter settings. Record this to another audio track then hard pan the two audio tracks left and right. This simulates the doubling techniques used by vocalists and guitarists for decades, and you don’t have to buy a second synth of the same model to get this effect.
Two Identical Synths Hard Panned
This is the method that I demonstrated in the “Total Stereo Immersion” video. I chose the Behringer Pro-800 analog synthesizer because it sounds amazing, has lots of knobs and switches, and is affordable enough for most musicians to own two of them.
The key to creating an immense stereo field with two identical synths is to send both of them the same MIDI signal. I did it by sending MIDI from a Studiologic Numa Compact 2x to a MIDI Solutions 1-in/2-out Thru box. This splits the MIDI to two MIDI out jacks. Each output was connected to the Behringer Pro-800 desktop synths. (In the video, I rackmounted the two Pro-800s so that one was directly above the other.) The monaural audio out from each synth was sent to the camera’s audio inputs (one to the left input, the other to the right input).
The stereo fields created with two nearly identical synths are so far beyond anything an effects pedal at the end of the chain can offer. Tweaking knobs and switches on either side, or both sides, results in head-spinning effects that are created by these left/right parameter differences. In short, this method provides the same kind of goosebumps you can get from far more expensive synths. (But hey, if you can afford two identical expensive synthesizers, then it will produce even more astounding results!)
Ready to Expand Your Sound?
If you have any questions about synths, effects, or DAWs that you could use to achieve a spacious stereo sound, or if you have your own special stereo methods to share, then we’d love to hear from you! Call your personal Sweetwater Sales Engineer at (800) 222-4700; with their passion and expert advice, you’ll be set to achieve a truly expansive keyboard sound.