In today's video, Wes teaches a non-trivial topic: time travel. Tactfully tackling a tricky task for building tracks on the Digitakt, Wes shows us just how twisted, turned around, and downright weird time can be.
Alliteration aside, today we're talking about time stretching, time compression, and the decoupling of pitch and tempo. Time stretching is a super important technique in the world of sample-based music, and yet, one of the world's most fully-featured and much-loved samplers (Elektron's Digitakt) doesn't have an obvious way to do it! But that doesn't mean that it isn't possible...with some clever programming and experimentation, there are workarounds to be found.
So, what's up with time stretching? Why is it so important? And how can you do it on the Digitakt?
Sampling Fundamentals: Pitch, Tempo, and the Tandem Problem
In the world of sampling—that is, the world of using recorded sounds as the basis of creating new music—you often run into a phenomenon sometimes referred to as the tandem problem. But what is it?
The tandem problem refers to the linkage between perceived pitch and perceived speed in sample playback. You might have noticed this if you've ever used a sampler to change the pitch of pre-recorded material: if you play a sample back at higher than its original pitch, the sample appears to be shorter than the original recording. Similarly, if you play it back at a lower pitch, it will appear to be longer than the original recording.
This is because, whether you're recording on tape or recording on a traditional digital sampler, you're not simply adjusting the pitch of the sample (that'd involve some kind of unknown magic). Instead, what you're actually doing is adjusting the playback speed. You can think of this like adjusting the speed of a tape player or a record player—not only does it affect how long it takes for the tape to play back, but it also affects the perceived pitch.
Early samplers didn't offer a solution to this problem...and for the most part, they didn't need to! Early samplers and sample-based drum machines for the most part had only enough memory to play back very short, one-shot samples. Increasing or decreasing their pitch would change their timbre and duration, sure, but since for the most part these were played as individual sounds with a keyboard or sequencer, it was okay—the sense of timing was really more about when the sounds were triggered more so than their playback speed.
However, eventually, as samplers gained greater memory and musical styles began to evolve around the expanded capabilities of these technologies, it became common for sample-based artists to incorporate longer samples...even samples of other music, much in the style of DJs and turntablists who preceded them. That's awesome, but suddenly the tandem problem became an actual problem: typically, it wasn't possible to adjust a sample's playback tempo without affecting its pitch, and vice versa. Especially when the tempo of a recording might not match the tempo you've set on your sampler, this can severely limit the possibilities of the medium—and it seemed that there should be a workaround. In fact, clever instrument designers did come up with a number of solutions—one which we can demonstrate using Elektron's Digitakt.
Oddly enough, Digitakt doesn't (as of the time of publishing this article) have a direct solution to the tandem problem built-in, as do some other modern-day samplers (which make adjustments to tempo and pitch seem seamless to the user). But that's not to say you can't do it—so, how can you do timestretching on the Digitakt without affecting the playback pitch? And how can you adjust the playback pitch without affecting the tempo? Wes's video above gives you step-by-step instructions on how to do this as well, but let's walk through the steps.
Step One: Set up your sample. Load your desired sample—try to use a sample of a short break, let's say a measure long. Set the sample start point to 60 (on Digitakt, a sample's beginning is position 0 and end is 120, so we know that 60 is cleanly in the middle).
Step Two: Set up your LFO. This is where the bulk of the trick lies. Set the LFO to a rising ramp shape. Map the LFO to sample start position, and set your depth to 60 (which, given our selected start point, gives us the full swing from position 0 to position 120). Set the speed to -8.00 (we'll discuss the implications of other values in a bit), and set the BPM multiplier to 4. Set the LFO to retriggered mode, but turn retriggering off on the Trig page.
Step Three: Set up your sequence. Set a trigger on all sixteen steps of a single-bar sequence. And here's an important bit: set a parameter lock on the first step to turn LFO retriggering ON for that step only.
When you press play, you'll be able to adjust your tempo without seeming to affect the playback pitch, and you'll be able to adjust the sample pitch without seeming to affect the pattern tempo, effectively decoupling these two parameters and sidestepping the tandem problem. But how does it work?
In short, with this technique, you're using the LFO to update the sample start position at the beginning of every step of the sequence. This means that up to sixteen times per measure, the sequencer is telling the sample where along its duration it should currently be playing, with respect to the current pattern tempo. If your playback pitch is higher than the original pitch, this means that on each step, the LFO sort of "kicks" the sample playback back to where it should be, and if your playback pitch is lower than the original pitch, the LFO nudges the playback forward on each step to help it keep up. It's crude, it's sloppy, and the further you nudge the pitch or tempo, the weirder it'll sound...but it actually works surprisingly well.
By changing the tempo multiplier and LFO speed, you'll be able to tell the sample just how much of it you want to map to a specific time duration on the sequencer. By changing these values, you could easily dial in half-time, double-time, etc. playback speeds using this weird, pseudo-granular technique. By changing LFO shape, you can scrub back and forth, randomly, backwards, etc. By parameter locking different aspects of the LFO, you can create truly scrambled textures—there's a huge range of techniques to explore beyond the simple pleasures of decoupling pitch and tempo.
Looking to get deeper? Don't worry—we'll be coming back with more Digitaktics in the near future.