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In this tutorial, I am going to describe how to synthesize a usable kick drum sound from scratch. I've attached a zip file containing five variations on my ownrendition of this sound, recorded as 24-bit WAV files. The variations are simplykicks of different lengths, and they are named, from longest to shortest: long,medium, short, razor, and micro. You will need a fairly sophisticated synthesizer to follow the tutorial; I used Sytrus. Included in the ZIP file are the FL Studio Sytrus presets for each variation of the sound.

This sound has three components: the click, the pop, and the body. The click andthe pop, sounding together, give the attack its character, with the click providing the treble of the sound, and the pop providing the midrange. The body is the longest-lived part of the sound, and it provides the bass. The only differencebetween the included variations is the amplitude curve of the body (e.g., "micro" has a shorter amplitude curve than "short"). We will now examine how to synthesize each component of the kick drum sound.

The Body

The body is a pure sine oscillator which changes in pitch throughout its life. It starts with a fairly rapid fall from a pitch in the low mid-range, down to a low bass pitch. From there, it will continue to more slowly fall in pitch for theremainder of the life of the sound, possibly dipping into the sub-bass range. Getting a good frequency curve is essential to making a good bass drum sound.

Having considered the body's pattern of frequency change, we must now consider its pattern of amplitude change. The 'traditional' choice for the amplitude envelope of a bass drum body would be a simple exponential decay, because this is what analog drum machines use. However, this choice would not be maximizing our bass drum's potential: we can give the bass drum a much greater amount of energy, with the same maximum amplitude, by giving it a more extreme amplitude envelope.For the bodies of all of the kicks except for the long kick, I used an envelopewhich simply stayed at maximum amplitude for most of its duration, then droppedoff fairly rapidly at the end. The observant will note that this is essentiallythe same sort of envelope one would get by applying extreme compression to a bass drum with an exponential decay; using a nonstandard envelope is simply a muchcleaner and simpler way to get the same result.

For the long kick, however, I didn't use this sort of envelope; I wanted a bassdrum that decayed gradually. Even so, I still didn't want to use an exponentialenvelope; instead, I used a linear envelope, thus giving me a sound which decayed gradually while still having a high level of energy, relative to its amplitude.

It's quite possible that your synthesizer does not give you this level of control over its envelopes. If that's the case, it's probably giving you plain old exponential envelopes, and I'm afraid that you will have no recourse other than tocompress your kicks.

The Pop

The pop is a sine oscillator with a very short decay time that performs a rapid,wide descent in pitch over its lifetime. It should sweep across the mid-range,in order to fill out those frequencies.

The Click

The click is made by a sine oscillator with a high frequency, frequency modulated by another sine oscillator, to create a rich spectrum of enharmonic frequencies. To find acceptable values for the two frequencies, just experiment until youfind a sound that fits well with your pop and your bass. My kick uses a carrier

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oscillator with quite a high frequency, and a modulator with a lower frequency.

For the amplitude, I chose to use a linear decay envelope. The decay must be extremely short; you're aiming to get just a simple 'click' sound, and nothing else.

Blending

Now that you have your three sounds, you need to mix them together. I found thathaving the click and the pop at about equal levels, with the body about twice as loud, gave satisfactory results. However, you are certainly not restricted inthis way, and choosing a different balance, particularly between click and pop,will give your kick a different character.

Fine-Tuning

After making my bass drum sound and looking at its waveform in an audio editor,I found that the initial amplitude was much higher than the amplitude throughoutthe sound, due to the summing of the click, the pop, and the body all together.Deeming this extra amplitude unacceptable, I added an imperceptibly short attack time to the body, so that it was at a low amplitude at the start of the sound.This fixed the amplitude problem with a negligible effect on the sound.

I also decided that my pop and my click had some undesirable low frequencies. Th

e pop had them simply because it decayed, over the course of its life, to a lower pitch than I had intended; the click had them because of the nature of the FMalgorithm. To remove the low frequencies from both of these sounds, I ran them through a high-pass filter.

This sound will work better if you have a synthesizer that resets its oscillators on each note trigger, rather than having free-running oscillators; that way, you get a completely consistent sound on each hit. If your synth has free-runningoscillators, I recommend that, once you've finished your sound, you bounce a number of hits to audio, pick the best-sounding one, and trigger it as a sample.

Expansion

You can take this sound in lots of different directions. Play with the differentfrequencies and envelope curves. Experiment with different methods of synthesizing the attack. Layer other kick samples over the synthesized kick. Process it with some effects. Et cetera. The point of this tutorial was not to give you a prescriptive method of synthesizing kicks, but just to give you somewhere to start, and something to elaborate on. The real point of the tutorial is this: if you're anything like me, then the idea of tweaking your own kick drum sound to perfection in a synthesizer just appeals to you more than trying to do the same thingwith samples.

Does anyone have anything to add, or anything I could do better?