Vocoders carry an unfortunate and undeserved reputation as a cheesy robot-voice one-trick pony, but this barely scratches the surface of their capability. They are in fact versatile spectral processors, woefully underused and misunderstood. In this article, we'll look at just one of the countless uses of Ableton’s Vocoder: using its noise source as a creative layer in drum sound design.
Softer, Brighter Hats
One of the great properties of the vocoder is that it inherently functions as an envelope follower. An envelope follower follows the contour of the input signal's amplitude, making that path a control for other parameters (in this case, the amplitude of the carrier signal). This makes it easy to create a parallel layer with new harmonic/timbral content, effortlessly matching the input signal's rhythm and dynamics.
Hi-hats are a particularly good candidate to layer with noise because they're pretty much just rhythmic white noise themselves. For this demonstration, I'm using a recording of acoustic hats from our Hi-Hat Pack.
As you can hear in the example, real hi-hats typically have a lot more midrange than electronic samples. I want to remove some of those frequencies but also mellow them out with layered white noise, something I wouldn’t be able to do with an EQ adjustment alone. The vocoder will impart a softening timbral effect while perfectly preserving the dynamics and groove of the acoustic drum loop - “playing” the white noise only when the hats are hit.
I started by adding Live's Vocoder and making sure the Carrier (the timbre-controlling signal) is set to "noise". The XY pad below the selector is great for changing the density and texture of the white noise, but I found only a minor tweak to this was needed in the case of these hats as I'm after the traditional white noise sound to blend with my hats.
Then it was just a matter of playing around with the settings on the device while listening at 100% wet. Since I was looking for a brighter sound with these hats, I pulled the Formants knob up so that the noise's frequencies are shifted upward.
The Depth control determines how strictly the amplitude contour of the input signal will be applied to the carrier, which can be thought of as how much influence the input signal will have on the dynamics of the carrier. I wanted to keep the noise tight with the original hat loop, so I've cranked the depth to around 136% to better match the hats' amplitude envelopes. I also set the Release to something close to the release on the hats I'm working with - a good starting place would be anywhere from 80 ms to 150 ms, but this will vary based on the original signal.
At this point, I switched my focus to the heart of the vocoder - the filter bank. Vocoders are essentially a bank of bandpass filters that detect amplitude differences in each band and dynamically copy this behavior to the filter bank affecting the carrier (white noise in our case). A lot of this will be trial and error, but for these hats I liked the sound of fewer Bands. I also made the filters wider (by increasing BW) and switched them to the grittier Retro setting.
It's a good idea to play around with the Range, too - this can make a dramatic difference in the unpleasant washy phase sound you might hear. For hats, my focus is on attenuating the upper range that can be rather harsh, so I discarded a lot of the low end information and increased the upper register. Then I drew over the resulting bands looking for the best balance.
Finally, I pulled back on the Dry/Wet knob to get a good mix of the original signal blended back in. The vocoder noise is rather quiet, so something around 75% should do. Once I hear the final result, I usually go back through the settings and tweak them, especially making sure the Release time on the noise matches and doesn't bleed past the hats.
Unmute the example above to compare the sound of the Vocoder on and off. The noise layer is much easier on the ears than the harsh, thick original loop and the softer sound will blend nicely into a mix.
Noise makes a good snare layer as well because it's essentially the sound snare wires produce. Envelope-shaped white noise even takes the place of a snare in some classic drum machines, so adding a layer with the vocoder will add an electronic feel to any snare sample. Here are the sounds I'm starting with:
The kick and percussion loop are from our Analog Drums pack and the snare is a generic acoustic sample. For this loop, I was looking for something a bit more icy and electronic, so the vocoded noise was the perfect tool for the job.
After placing the vocoder on the snare track, I started adjusting the dials again. I thought the noise could be just a little brighter, so I made a very slight clockwise adjustment to the Formant dial. The real focus, however, is on the Release, which I turned up to 750ms for a nice decay on the noise.
With the envelope about right, I made timbral changes with the filter bank. I've found that the lower and wider Bands set to Retro work best for the purer white noise sound I've been going for with these percussion examples. For the snares, I allowed considerably lower frequencies through in the Range than I did for the hats, ensuring the fundamental is captured by the vocoder.
After pulling back the Dry/Wet to add some of the original sound back in, this is the result. It has the feel of a vintage drum machine and adds some much needed brightness and decay to the snare sample. You can hear the difference in the above example as the snare switches between dry and vocoded each bar.
Mixes often have the problem of the kick becoming buried and muffled. A kick is generally built of two parts - the thumpy bass and the click. An indistinct kick is often the result of the click not doing its job very well. One could add more of click by manually adding a sample to each bass drum, but since we'll often be looking for a white noise-esque sound anyway, the vocoder is a great tool for adding this automatically.
Here's the loop I'm using. In this state, the kick must be made set quite high to be heard, which doesn't sound great with its muddiness and overly-round tone.
If you try loading a vocoder on a drum like this, you'll notice it sounds pretty awful. This is because the heavy bass doesn't translate well to the white noise and by default the Release time is quite long. I know that I want this synthesized click sound to be very tight, so I'll bring the release down to just 50 ms and raise the Depth quite high as well. Then I'll make the usual small adjustment to Formant and modify the noise source to be a little less bright.
The biggest strides are made in the filter bank, as usual. I want to ignore the bass frequencies of the kick as my focus is on the click, so I drew across the filter banks to reflect this. Because there is so little information in the mids and highs of a bass drum - and particularly in this muffled one - the vocoded click is quite quiet, so I boost it using the Level gain control.
The audio example shows the difference after the synthesized click has been added with the vocoder, as it switches between dry and wet each bar. The kick itself becomes more defined, and you can tell that this will cut through a dense mix better as well.