Empress Blog

Transform Your Patches By Using a Sample and Hold May 20 2022

Sample and Hold

What it is and 5 ways to Transform Your Patches Using One.

19th May, 2022 - John Peippo

My fascination with sample and holds began with a Crumar DS-2. When I first laid hands on this distinctive Italian synthesizer, I noticed it had something I had never seen before: a staircase LFO. One of my friends who shared my passion for vintage synthesizers mentioned that the Crumar was "sampling a sawtooth waveform" to create the unique shape. At the time, I didn't really grasp the concept, but when the Euroburo came out, one of the first things I wanted to do was create a staircase waveform.

Before we jump into staircase LFOs and all the other unique ways sample and holds can unlock your patches, let's try to answer this question....

Just What is a Sample and Hold?

It may not be evident at first, but what a sample and hold really does is suspend time. It's a time capsule, holding onto the past while the world moves on around it. And it can seem alien at first because we often think of time as fluid and continuous. So to understand sample and holds, I want to use the analogy of a camera -- another type of time capsule.
If we take pictures fast, like thirty frames per second, we have a movie. If we slow down how often the pictures are taken, what looks like continuous motion begins to feel more herky-jerky. Once-fluid actions become periodic motion; a person starts getting up from a chair, and the next thing you know, they are halfway out the door. A sample and hold is like a camera, too: its input is the lens, taking in whatever it is pointed out; its trigger is the shutter, determining when to snap a shot of that view; and the output is the photograph, our moment frozen in time -- until the next photo.

Getting started using a sample and hold to make a Staircase waveform

We can take our "photos" (sample our inputs) really fast, or really slow, or really herky-jerky, too. To illustrate this, let's patch up that staircase waveform.

To get started, we'll need three things:

1. A sawtooth LFO.

2. A square LFO.

3. A sample and hold.

Since we want to freeze our sawtooth -- take its photograph at various times -- its output will be connected to the sample and hold's input. We're going to use the square to work as an automatic shutter, timing when those pictures are taken at regular periods, so we will connect its output to the sample and hold's trigger input. Each time the square rises -- sample and hold trigger (sometimes called clock) inputs look for the rising edge of a pulse or other CV signal -- it will trigger the sample and hold, and the current position of the sawtooth (the sample) will be frozen (the hold) at the sample and hold's output -- our collection of pictures that will add up to a staircase LFO.

If you just loaded the modules in their default condition and connected them, you're probably looking at that output and thinking: something's wrong, I don't see a staircase at all, just a straight line.

That is because using a sample and hold is all about timing. Since the sawtooth LFO and the square LFO share the same default rate, we're taking our pictures of the sawtooth LFO at the same position each time.

If we speed up our square LFO, we start to take pictures at a faster rate than the sawtooth LFO cycles, so the sample and hold's output begins to change. At first, though, it may not be very clear what shape we're sampling -- if the square wave LFO is only a little faster than the sawtooth, the samples may seem to jump around as they catch the sawtooth in a pattern that isn't immediately obvious. That's jbecause one way to think about the speed of our square is as a fidelity control. Right now, things are pretty lo-fi, but as we increase the speed of the square, the sawtooth begins to take form. When it is about four times as fast as the sawtooth, we should really begin to see the staircase form. As we increase the speed more, our staircase has even more steps to descend. And then, a funny thing begins to happen. As our fidelity increases, there are more and more steps, and the steps are smaller and smaller. Our sample and hold's output is looking a lot like a sawtooth wave again, maybe a little bumpier than usual, but definitely more sawtooth than staircase.

Of course, you can apply this technique to more than just sawtooth waves. Make your envelopes chunky! Turn an envelope follower into staircase follower! You can even modulate the sampling rate -- in our example, the rate of the square LFO -- to switch between smoother and more steppy forms, or you can use an irregular timing source to produce more unexpected results.

If this sort of waveform manipulation interests you, you might also look at the steps module in ZOIA, which takes continuous CV sources and breaks them up into discrete, even steps. A very similar process, but achieved by slightly different means.


5 More Create Ways to Use Sample and Holds

There are countless applications for sample and holds, but let's talk about a few more before I leave you with some resources.

Sci-fi Effects

Probably one of the most well-known uses of sample and holds is to create the beeps and the boops of classic sci-fi robots and alien technology. In this case, the sample input is usually white noise because it provides a source of random frequencies. When you clock the sample and hold, the output is a sequence of steadily changing voltages.

Hooked up to an oscillator's frequency input or a filter's cutoff frequency (or used with a ring modulator, or a delay line, or... the list goes on), you can quickly discover a whole world of classic sound effects and some new ones, too (like in the staircase LFO example, try modulating the clock speed!).

You can do the same thing in ZOIA by connecting a random module to the input of a sample and hold. But the random module itself has an option to produce a new random value only when it's triggered -- the same effect with fewer modules!

Generative Melodies

It's not such a great leap to get from a string of random frequencies to a generated melody. Really, we just take the example above, constrain its range with some attenuation (you might want unexpected notes, but you don't want them all over the place), and then quantize the results.

You can get more elaborate, too, using shift registers (which can be constructed in ZOIA using sample and holds strung together) or CV loopers or logic to make the randomly generated melody feel more purposeful and focused.

Delayed Trigger

Because the output of a sample and hold won't change until it receives a trigger, they can be a great way to get your patches' ducks in a row, so to speak. For instance, you could use the clock from a sequencer to change several other parameters at the beginning of each step; just use it to clock the sample and holds placed between a modulation source and a destination.

Or you could use the output of a clock divider to have those changes happen in some ratio of the sequencer's clock, like adding a "strobing" effect to filter frequency changes by using a sine wave as the sample and hold's input and multiplication of the clock to trigger the sample and hold!

Sample Rate Reduction

You might remember that I mentioned earlier how the clock rate of a sample and hold acted as a sort of fidelity control. We can take this even further in the audio realm by using an audio rate clock -- like a square wave VCO -- and sending audio to the sample and hold's input. The frequency of the clock will determine the sampling rate of the audio, so you can really use this to add some dirt and crud to a single. It's loads of fun! Your sample and hold module needs to be AC-coupled to accept audio signals, but a lot are.

ZOIA's sample and hold doesn't accept audio signals, but that's what the aliaser module is for! It can perform the same kinds of sample rate reduction. You can even get sample rate reduction by modulating a VCA with a super-fast LFO (try using a clock divider to push the LFO speeds into low audio ranges).

Freeze Modulation in Its Tracks

A close cousin of the sample and hold is the track and hold. Unlike the sample and hold, which won't change its output until it receives a new trigger, the track and hold will allow the input of the sample and hold to pass to its output until it receives a gate -- a sustained voltage -- at its trigger input. Then, it will hold onto the voltage that was at its input when it received the gate, just like a sample and hold, until the gate ends, at which point the input will be passed to the output again.

You can use track and holds -- and the sample and hold module in ZOIA has a track and hold option -- to stop LFOs and other modulation sources in mid-cycle, essentially freezing them in place until you release the gate. It's a lot of fun and an interesting alternative to the staircase example we started with!

If you want to learn even more about all the things you can do with sample and holds, I really recommend DivKid's video:

Alex from WMD Devices also has a great video on some of the creative ways you can apply sample and holds:

John Peippo

John does assembly, customer service, and repairs at Empress. Check out John's music with Polonius and Klapsmock.

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Polyphonic or Monophonic? What is the difference, and which option is right for you? April 20 2022

Polyphonic or Monophonic?

What is the difference, and which option is right for you?

20th April, 2022 - Christopher Jacques

So, you've been scoping out guitar synth pedals. Or maybe you're ready to make your first (or fifth) synthesizer purchase. Perhaps you've gone down the eurorack rabbit hole and are browsing for that one last module to complete your rack. (Don't worry; there's always another rack.)

You've probably had some version of this debate: monophonic or polyphonic; which one to choose? So let's look at that question, beginning with what those two words really mean and concluding with some ideas for how ZOIA can be used for either.

What is Polyphony, anyway?

Before we go any further, let's define these terms a little. They're more slippery than they first appear. (Ask Marc Doty, whose epic series on polyphony is linked at the bottom of this article.) We can get a basic understanding if we put on our philologist (word-knower) hats. From the Greek, mono means one; poly means many. Phony means voice. So, polyphony is many voices, while monophony is just one voice. A choir or a soloist.

But what is a "voice" when discussing synthesizers? Attempting to define a voice is where things get slippery. Some people describe the difference between monophonic and polyphonic synths as the ability to play chords. Except, many monophonic synths have multiple oscillators, which can be tuned to the intervals of a chord. Then, they might clarify that it's about being able to play different notes on a keyboard simultaneously.

However, if we look at a eurorack module like Mutable Instruments' Rings, it can play multiple notes at once, just not at the same time. So is it not polyphonic? You can see how this seemingly simple question has a lot of complicated answers.

While debates about those complicated answers will continue to rage on despite our best efforts, I'd like to present the difference between monophonic and polyphonic in the way that I have come to think of it. And that is in terms of expression. To make this even more precise, let's do away with notes and chords for a moment and speak only of sound (after all, some synthesizers strive for the atonal).

A monophonic synth allows you to express one sound at a time, while a polyphonic synth can will enable you to express more than one sound simultaneously.

Suppose we return to our example of the mighty multi-oscillator synth, one not so different in my imagination from the vaunted Moog Model D. In that case, we see that while it can form chords from its arrangement of oscillators, it can only express one chord at a time. Resoundingly monophonic. Meanwhile, the Mutable Instruments' Rings is restored to an untroubled position in the pantheon of polyphonic instruments. While only one of its voices can be triggered at a time, those voices can overlap and express different sounds simultaneously.

Monophonic vs. Polyphonic: Which One is Better?


We return to our conundrum with definitions in place: do we choose a monophonic synth or a polyphonic one? At first glance, it might appear the choice is simple. More is always better, right?

Context is critical here. Polyphonic synths and monophonic synths can serve different purposes, and it is often the case that the limitations of one are advantages of the other. I used the example of a choir and a soloist before. The choir can make beautiful harmonies, but it can't take the lead like a soloist can. So, while polyphonic synths excel at pads that fill the sonic spectrum, they can be less suited to leads that cut through that space.

I used to play bass in an R&B band, and figuring out where I sat in the mix with our keyboardist was a constant struggle. He liked to play a lot of chords with an anchor in the low end, and the bass would get lost at times. I would counter by adding fuzz or a synth pedal, but the added harmonics could crowd out our guitarist. (Our singer, meanwhile, continued to do what he did, blissfully unaware of the ongoing war for the mid-low frequencies. Ah, the life of a singer.) So my point is that there are times when filling space is useful. But there are also times when it is decidedly not.

The style of play also matters. The limitation of one voice becomes an advantage when you consider things like legato passages, where you want to smoothly glide from note to note. The same can be true of staccato passages, where too many voices at once can sound busy and confused.

More is often better, but there's a reason I'm perfectly happy with two legs instead of three. So, it really does come down to context. Every lock has a key, and sometimes a polyphonic key is the wrong fit for that particular musical lock.

The ZOIA of it all

Music has a lot of locks, so to speak, so sometimes the answer is a skeleton key, like ZOIA. A ZOIA patch can be a monophonic synth, a polyphonic synth, or even a combination.

Over MIDI, ZOIA can be a versatile polysynth. For example, the MIDI note in module supports up to eight notes at a time, each with its own pitch, gate, and, optionally, velocity output. However, it should be noted that while it is possible to make a patch that utilizes all eight of these outputs, there is often a compromise between the number of voices and their complexity.

If you want to use FM, for instance, then the number of oscillators you need doubles (or more), or if you're going to employ ZOIA's effects, each of these additions may mean compromising on the number of voices at your disposal. On the other hand, if you are designing a monophonic patch, you may run out of ideas long before you run out of CPU.

When used as a guitar synth or employing the CV inputs of Euroburo to control a synth, it may seem like you are limited to monophony. After all, the pitch detection on ZOIA is monophonic; there are only so many CV inputs to utilize. But suppose you use triggers, rather than gates, to control the envelopes of your voices. In that case, you can trigger overlapping voices to play simultaneously, much like how Mutable Instruments' Rings employs polyphony.

Of course, ZOIA has many internal methods of producing sound, from sequencers to generative approaches, and these can also have monophonic or polyphonic applications. Moreover, these can be combined with the previous methods to create patches that are more than just monophonic or polyphonic; they are multi-timbral. (Multi-timbral is just synth-speak for producing two different types of sound at once, like clapping while you play the kazoo. Or, arguably, something more aurally pleasing than that.)

This isn't to say ZOIA is the best answer to our initial question. There are many options for synthesizers and synth pedals out there, and plenty of them do things that ZOIA can't. (I've opened up the enclosure before, and there is no fold-out keyboard tucked inside.) Variety is the spice of life. But it may be that ZOIA is an answer that you've overlooked and is more versatile than you first imagined.

Introductory video to Marc Doty's exploration of polyphony

Christopher Jacques

Christopher Jacques is a West Virginia-based musician, sound designer, and ZOIA expert. He designed the majority of the ZOIA Euroburo factory patches and shares many more on patchstorage.com. Christopher also shares much of his knowledge in the ultimate ZOIA resource in the ZOIA Tips and Tricks document and on his YouTube channel.

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Expression Pedals:
What They Are and How to Use Them

Expression Pedals April 07 2022

Expression Pedals

What They Are, How to Use Them and the Top Choices for Guitarists

7th April, 2022 - Michael Hahn

Expression pedals are the key to controlling your effects in real-time. They make it possible to adjust the knobs on your pedals in sync with your playing.

But there is a vast range of approaches to using expression pedals in your rig. So it can be hard to know where to start if you haven't tried one before.

This article will explain how expression pedals work, suggest six creative ways to use them, and break down the recommended choices for every budget.

What is an expression pedal?

An expression pedal is a foot controller housed in a rocker-style enclosure that lets you change effects parameters on the fly.

By varying the pedal position between heel and toe, you can simulate the effect of turning a control with your hand in real-time.

Expression pedals are named as such because they're used to add musical expression to static sounds and create change over time that enhances a performance.

Mechanically, an expression pedal is a simple device. In most cases, expression pedals consist of a single passive potentiometer with a TRS output connection. Some designs offer multiple outputs, configurable ranges, and other features, but they all perform the same essential function.

In a typical setup, you connect the pedal's output to an expression control input on your effect. Different pedals offer various configurations for controlling their parameters, but I'll get into that below.

Why use an expression pedal?

Changing effect controls on the fly adds a new dimension to your playing.

After all, sound texture is a vital part of any musical arrangement. Emphasizing a passage with effects is a powerful trick for building intensity and atmosphere.

But controlling specific parameters can take it even further. For example, there are endless ways to create drama with a well-timed adjustment to your sound's timbre.

Not only that, some effects depend on manual control to create their signature sound.

For example, you're probably familiar with the most common expression-controlled pedal—wah. However, the vocal quality of the effect relies on manual sweeps of the filter that match your playing.

If you've ever wished you had a third hand to tweak your pedal settings as you play, expression pedals can give you the flexibility to play your effects like an instrument.

Setting-up expression control on the Echosystem is easy. Dan demonstrates above on That Pedal Show's Expression pedal episode.

Five creative ways to use your expression pedal

Expression pedals can be set up to control just about any parameter you want. Depending on the capabilities of the pedal you connect them to, you may be able to choose from many different options.

I’ll break down five common ways to use expression pedals and explain the results they produce to give you some ideas to get started.

Wet/dry blend

The blend of wet and dry signal determines the overall strength of ambience effects like delay and reverb.

Varying the wet/dry balance with an expression pedal can create contrast between sections, or provide a textural effect at extreme settings.

Controlling wet/dry mix is as simple as moving the expression pedal to the heel position and setting the mix control fully counterclockwise. Hold the save button to assign the expression value to the heel and repeat the process with the mix control clockwise and the pedal in the toe position.

Now you can gradually fade in washes of ambience that obscure your dry signal completely at the highest setting.

Delay oscillation

Who doesn’t love the classic runaway delay oscillation effect? When it’s a great vintage-style delay, the unique distortion and wailing trails are always fun to play with.

When you adjust the delay time, the oscillation pitch changes as the signal feeds back into itself.

The Echosystem’s tape mode can be configured for expression control of the delay time parameter. With the feedback set high enough you can use the expression pedal to “play” the pitched oscillation of the delay, even as you play new notes into the feedback loop.

It’s a great way to get musical wails and unpredictable pitched feedback as you play.

Modulation speed and depth

Modulation is a broad category of effects pedals.

Despite the different styles, this effect type almost always relies on an LFO to control the speed and depth of its action.

LFO stands for low-frequency oscillator. This waveform is so slow that you don't perceive it as a musical tone. Instead, the LFOs frequency, depth, and waveshape define the character of a modulation effect's sweep.

Changing the rate or depth of the LFO sweep with an expression pedal has unique effects for different modulation types.

For example, setting an expression pedal to control the Empress Tremolo 2's rate lets you ramp up and down from a shaky stuttering effect to a slow pulsing tone.

Johnny Greenwood famously used this technique in the rhythm guitar track on "Bones" from The Bends.

Pitch shift

Another classic rocker-controlled effect is the dive-bomb pitch shift made famous by the Digitech Whammy.

The original pedal comes with a rocker treadle built-in, but it's large, heavy, and requires a high current power supply.

If you don't want to devote all that pedalboard real estate to a full-size whammy pedal, you can accomplish the same effect using an expression pedal and a compact pitch shifter like the EHX Pitch Fork.

Multiple parameters

Several of the best expression pedals feature additional outputs to control two or more parameters at once.

Sweeping the range of multiple controls creates a morphing effect that blurs the parameters together.

Also many digitally controlled pedals allow for control of multiple paramaters at once. The Empress Reverb and Echosystem offer comprehensive parameter control via expression pedal. In fact, you can blend between two positions on every knob as you rock the expression pedal from heel to toe.

The ZOIA is inspired by the flexibility of modular synthesis. It offers expression control of nearly every parameter in any combination and direction!

If you're looking to create evolving textures with hands-on control of a whole chain of processors, there's no better way than with ZOIA.

The control port on the Reverb, Echosystem and ZOIA can be used for

expression pedals, MIDI, an external switch, tap tempo, or CV.

6 Great expression pedals for guitarists

 If you're in the market for an expression pedal, there are plenty of great options to suit any budget.

Here are six top picks to get you started.

Moog EP-3

The Moog EP-3 is a cost-effective and well-built expression pedal. It features a single output and comes with a 6" TRS cable if you don't have one on hand.

The EP-3 is among the most affordable choices on this list, but its construction is mostly plastic. Keep that in mind if you need a more roadworthy option but I've had one for years that has taken a beating and works flawlessly.

Mission Engineering EP-1

Mission EP-1

Mission Engineering takes expression pedals seriously.

They have a vast line of options that cater to the specific expression needs of popular modern gear.

The standard EP-1 model is a solid all-around choice in a familiar full-size wah style enclosure.

Boss FV-30

Boss's latest take on rocker-style pedals is a robust all-metal design that feels great underfoot without taking up too much space.

It features dual outputs for controlling two effects at once and range controls to set the boundaries of the sweep.



Source Audio SA161

Source Audio's SA161 is another great dual output expression pedal with solid build quality and multiple outputs for controlling two different parameters.

Dunlop DVP3

Dunlop DVP3

If you're looking for a pedal to work as a volume pedal and an expression pedal in a compact package, the Dunlop DVP3 is one to consider.

It offers a durable design with adjustable rocker tension for the perfect feel.


Any Volume Pedal

Speaking of double duty, any volume pedal can act as an expression pedal if it’s connected with the right type of cable.

The one you’ll need is a ¼” TRS to dual ¼” TS cable. These are sometimes called insert cables because they’re used to add pro audio gear like compressors to the signal flow of a mixer.

With the tip TS jack plugged into the volume pedal’s input and the ring TS jack in the output, your volume pedal will behave just like a TRS expression pedal.

Michael Hahn

Michael Hahn is a Montreal-based musician, music writer and engineer at Autoland Audio

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