S&H: VERY different from S&M, it turns out, but still interesting
Sample and hold (S&H from here on out) is a concept that’s often misunderstood (and, because of this misunderstanding, the name is often put on things that are not, in fact, sample and hold). Let’s demystify the concept, and talk about some creative uses!
So, what’s it actually do, then?
The name is actually pretty descriptive here, which is nice. S&H circuits generally have a CV input, CV output, and trigger input. Every time it receives a trigger at the trigger in, it samples whatever CV value is at the input and outputs it continuously, until it receives another trigger, and then repeats the process. Sounds funky, but it’s pretty simple when we look at it visually, so here’s a picture:
We have a stepped CV sequence and some triggers going in, and sampled CV coming out. Pretty straight forward, and useful for a number of things…
The most common use, and the main reason S&H is misunderstood: random
In the context of an oscillator, noise is just random voltage. When paired with a S&H circuit, we can create random voltages at will every time we send in a trigger. This is such a common patch that many sample and hold modules have noise generators built in (for instance, the Industrial Music Electronics IME1987). Because of this, it’s common to think that S&H modules are just for random voltages, but there are a lot more uses beyond this simple patch.
Speaking of melodic uses, if you have a synth line, you can easily create a sort of harmony with a S&H, a clock divider, and another voice. Mult your 1v/8va signal from your melody to the CV in on your S&H, too, and trigger it with a clock that’s much slower than your melody, like /16. Patch the CV out of your S&H to another voice’s pitch input and you have a harmony based off of what your melody is doing.
Here, we’re using Mimetic Sequent. With the Record switch all the way up and the Random knob all the way down, it performs just like a normal S&H. We’re taking a copy of a 15 step sequence from Vox Digitalis, and sampling it every 16 steps to create a nice harmony. Our main melody is Basimilus Iteritas Alter through the upcoming Desmodus Versio, and Ataraxic Iteritas is the bassline.
When sent audio-rate triggers (think a square-wave oscillator) a S&H module can become an interesting audio effect. Run audio through the CV in and monitor the output. We’re literally changing the sample rate of our audio which creates some very interesting effects, fun for drums and synths and the like. And, if you’re using it on a synth line, patch your 1v/8va signal to the triggering oscillator, too. If tuned nicely, this will give you melodic sample rate reduction, which sounds really cool.
Quick note: not all sample and holds are great for pitch
As with a lot of things in eurorack, your mileage may vary when using S&H modules for pitch duties. Some are more accurate than others, so be prepared to retune and stick a quantizer after your S&H module if it doesn’t perform super accurately.
Related: Track and Hold
You may have also heard of something called track and hold (T&H). It’s a bit less common; in fact, I only learned about this circuit because I had a Doepfer A-184-1 which has a switchable S&H/T&H section in it. T&h is a different-but-related function that works similarly to a S&H circuit. It has CV in and out like a S&H, but a gate input instead of a trigger in. When the gate is low, it passes whatever CV is input directly to its output. When the gate goes high, it samples the CV at its input at that exact second and holds it until the gate goes low again. Which looks like this:
Get a bunch
S&H is one of those functions that, once you start using them, you’ll probably want a lot of them. I use Mutable Instruments Stages for this a lot, but if you want something a bit simpler, the Doefper A-114 is a popular and straight-forward choice.
Get creative! S&H (and T&H) modules have lots of uses, even outside of what we’ve discussed here, so try them out in your patches and see what happens!