Tempest Recipes: Bass Drums Part I

There are three basic types of Bass drum.

1. Kick drums, as seen on typical drumkits and the classic drum machines. Generally more punchy than…
2. Large orchestral drums such as the Timpani (kettle drum), and…
3. Pitched bass drums, played in pairs or more that are tuned to different pitches. The Brazilian Surdo is my favourite drum, so I’ll particularly interested in synthesizing that.

Let’s look at a few ways to approximate the more ubiquitous kicks. I will use the famous Roland bassdrums as guides. The aim of these exercises is not perfect emulation, but understanding. I do not own, nor have I ever owned, one of these instruments.

808 Kick:

A real 808 kick is essentially a triggered resonant circuit with a short frequency rise at the beginning (Attack). It is said that no two 808s sound alike; there are variable settings of the internal trimpots along with good-old analogue mojo. So the sample provided is representative only. I selected one that was reasonably defined and long-enough to be distinguishable. This one is rather high pitched too.

Download: 808_BD_Raw

Because sound changes over time, I provide two spectrum views of this sample, (but really – you should do this yourself in real-time).

Beginning:

End:

We can see that the fundamental of the sound is around 60HZ (x-axis-frequency, y-axis=amplitude).

This sound is often approximated by using a sine wave modulated by a pitch envelope – the ‘pitch drop’. At low values with a long decay the sound is deep and ‘floppy’. At higher values with a short decay the sound both tightens-up and increases in pitch. Lots of possibilities already exist through balancing the Oscillator pitch and Pitch Envelope amount. It’s a simple concept but already opens up whole world of Kick drums – generally, for more ‘punch’, increase the intensity and duration of the pitch drop. This would be an excellent place to begin your own experimentation.

Listen:  Pitch-dropped sine (130.81Hz – Osc 3)

We’re already in the general area. It at least shows us the importance of the pitch envelope is shaping the overall sound. Think of it this way – as the Pitch envelope amount increases and Decay gets shorter, it’s like tightening-up a real drum head. It can easily be adjusted to be loose or punchy. Try it for yourself.

For now our example still sounds dull and lacks the snap and clarity of a real 808. And there is another consideration here: In the graphs above, we see that the fundamental doesn’t move – it stays at approximately 60Hz throughout the sound’s life. This suggests either that there is no pitch-drop in action here, or that it is very abrupt. There is no noticeable pitch-sweep from higher to lower frequencies, which would indicate the influence of a pitch envelope.

Putting that aside for the moment, we could continue by trusting our ears and tweak around this basic setup. The initial snap is typically modelled by setting the sine oscillator phase to 90%. As the oscillator starts there is a noticeable click that sounds very 808.

But there is no oscillator phase control on the Tempest, so we could look to achieve something similar by adding our own short impulse. A low-volume square wave with the amp controlled by a very short envelope (Aux1) often works, using the filter to remove the highest frequencies.

Another more efficient possibility is to use an Aux envelope as a much shorter and steeper second pitch envelope affecting the attack of the sine.  Here’s where things can get get interesting. The primary pitch envelope gives the overall slow down pitch while the shorter, more extreme envelope provides much of the initial energy. Try it. Even add a third pitch envelope. Oh yes.

If you’ve been experimenting to this point then you will probably be far from 808 territory by now. But it feels good, no?

Back to business. Remember we saw no evidence of pitch envelope in the 808 sample? Well can try a common approach and get even better results using just the filter alone – no oscillators – and still stay in fully analogue domain.

The filter on the Tempest is self-oscillating. i.e. at low cutoff and high resonance it produces a pure analogue sine wave. This can even be played chromatically with the keyboard by applying keytracking to the  filter cutoff. On the Tempest look to the Modpaths menu – map note number to filter cutoff at a setting of 127. Close the filter completely and keep resonance at around 90. Makes for lovely, theramin-y lead sounds.

OK, so making a kick drum using only the filter:

• Start with an initialised patch – turn all Oscs off.
• Close the filter cutoff completely and set resonance to 90. Careful here – this will cause self oscillation – if you now open the filter cutoff too much your ears will hurt. So…
• Slowly raise cutoff until you can hear the beginnings of a short click and boom (Cutoff=40). Leave it there and…
• Begin turning-up the Filter envelope amount. The sound should become more snappy and ‘kick like’. What’s happening here is that the filter cutoff is now controlling the pitch of the Kick, while the resonance controls the length of the ‘boom’.  The Filter envelope quickly opens to give a high-frequency burst, before closing (according to your envelope decay settings) to give the deeper body.
• The cutoff envelope is the key controller here, and a good variety of usable kicks can already be had from the relative balancing of cutoff and it’s Envelope, especially  the decay setting. Keep you eye on the spectrum!
• Add a little filter FM (Audio Mod). Although there is no waveform loaded in OSC1 (and thus no FM Modulator), increasing the Filter FM makes the sound appreciably more boomy, giving a nice sustained  tail (assuming you have increased the Amp envelope to let it through). It does change the overall pitch so you may need to lower the filter cutoff to compensate.

This is a solid basis, but to take it further in emulating 808 and far far beyond, there is plenty of scope for more experimentation.

• Make the Attack more interesting: Use a digital square wave controlled by Aux env1 with a very short delay. The envelope is mostly closed as it is making the body of the sounds, however you can bypass the filter with the digital oscs. Just a little, barely perceptible, can give the sound more definition and ‘interest’. Exchanging the square wave for other digital Osc samples can lead to nice surprises. Hihats and hi-pitched congas can help a kick cut through the mix.
• Give it some wobble: – attach an LFO to the filter cutoff. Big boomy drums have vibrato that changes over time, tending to get faster but less pronounced. Model this by controlling the LFO rate with an Aux envelope, and controlling the LFO amount with the same envelope, but with a negative amount. Takes some subtle tweaking, but can give fantastic results. It’s just a bummer that Tempest’s LFO’s have no phase control, otherwise they could be used effectively as ‘one-shot’ envelopes.
• Inject some noise:  A tiny bit of white/pink/green noise applied post-filter can provide more ‘beef’ and definition.

909 Kick: 

The 909 kick uses a triangle oscillator, with a filtered noise click for the attack impulse. OK, it’s more complex than that, but we all know it’s character, so we trust our ears to guide us.

The aggressive sound of the 909 kicks that we hear on recordings is often more due to heavy post-processing – distortion, eq and brutal compression . So we have to be realistic. Tempest kicks do respond beautifully to external compression.

As a basic marker, here is a raw 909 kick.

What can we say about this dry sound apart from ‘it sounds pretty disappointing for a 909?  To compare – Here is one run through an outboard compressor. Or listen to any of your favorite early 90s house records. The difference is processing.

Looking at the raw sample we can see that the fundamental is at around 60HZ, similar to the 808 BD. It also has a lot more pronounced higher harmonics which give ‘brightness’.  A close listen confirms this. The tail is less boomy than the 808, and most of the low-end energy is concentrated in the attack with a quick decay. It almost sounds as if there is a very fast vibrato on the sound. The tail is also quite noisy.

Let’s see where we can get:

• Starting with a triangle in OSC1 Mix 100/0, wave reset on, key tracking off – fundamental around 60Hz (A2).
• Pitch to Osc1 freq only. Dcecay 24, Amount 90. This already gives us a pretty punchy and quite usable sound. But still a bit buzzy for our purposes, so lets use the filter…
• Filter cutoff=55.  Env amount=70, decay=60. Play with cutoff. Add a little resonance if needed. We want the filter to give a good snap, but leave the filter and Amp open enough to let the boom of the tail through.
• This sound is a gateway to a whole world of punchy and natural bass drums. There is a suggestion of plastic skin being hit, and it’s overall pretty snappy and rounded to my ears.
• Let’s bend the envelopes for extra impact. First, increase both the Amp and Filter envelope decays to 100 so we can appreciate this effect. In the ModPaths menu, set the Filter envelope to modulate it’s own decay and listen for the difference between positive and negative modulation. In this case I opted for a a setting of +50.
• It’s a good idea to the shorten the Amp envelope to account for the new filter envelope shape.  Here I set it to 90. Alternatively you could also bend this, but less severely than the Filter envelope.
• For a fat sound – open the filter some more 😉

OK this is nice, but needs still more dirt in the attack. There are several ways to do this.

• The simplest is to add some noise. Only a tiny amount is needed – a mix level of <10 from the Osc3 should be more than enough – just barely perceptible but makes a difference. White noise works well, but on the Tempest there is a pitchable noise sample (Resonant 4k noise) which gives extra flexibility. Mapping the pitch envelope to this noise sample gives good results – using both positive and negative values in the ModPath. For more precision, control Osc3 amp level to an auxiliary envelope with a short decay. Also experiment with adding a  small amount of attack to this envelope. The noise itself is barely distinguishable, but it does add somewhat to the overall impact and punchiness.
• Keeping it all in the  analogue domain, we can forget about the noise and introduce Osc2 instead.  Remove the noise for now and replace it with a short impulse from Osc2. The Osc mix setting remains at 100/0. Osc 2 as a saw wave pitched above the triangle causes enough perturbance in the attack to give that extra oomph.
• Use Amp Feedback. As you slowly turn this up the character will change – much more aggressive, easy to overdo. Control it with an envelope for more precision.
• If you are using separate outputs, assign the kick to a voice and route it through the main out. This way you can use the compressor for extra snap, and the distortion to get as dirty as needed.

Now add some noise back-in, but this time use pink noise with no modulation, and only a tiny amount (<10). At this stage you will have a a kick with a 909 character – probably not a replica of our guide sample but probably much better ;).

To extend this further, experiment with introducing different samples to Osc4. Many modern dance kicks have been layered from several samples. For example, a hi-hat controlled by a very abrupt envelope, barely noticeable, can really help a kick cut through. Try different samples, pitching them up-and-down as you go. Trust your ears.

These kicks should sound fundamentally the same – only the attack is different. But you can quickly tune them to your needs by pressing and holding the Oscillator select button. this will allow you to tune all Oscillators simultaneously.

You want my opinion though? The 909 kick is old-hat. The kicks that can be coaxed from Tempest are way, way, waaaaay more interesting.

In Bass Drums Part 2 we’ll build a flexible template using all 4 oscillators.