Let me start this blog post by apologising for my lack of words on digital paper over the past few months. Life got in the way a touch too much with a change in jobs and numerous video game projects starting which have occupied all of my free time. It is very nice to now be in a position to share some knowledge (however limited it may be) with yourselves again.

This post is going to address what I, as a drummer, consider the grounding force of any track, the kick drum. As well as discussing the kick drum and how to create them utilising FM synthesis, tom toms, the nature of which are very similar to kick drums will also be covered.

Tonal Characteristics Of Kick Drums & Toms:

Let’s dive into this post by thinking about the typical characteristics of a kick drum. In a lot of modern music the kick drum, along with the bassline, is the root of the track. Together they provide the backbone of many productions, helping to drive compositions along and provide a strong foundation for the rest of the production to be built upon. The same can also be said for chiptunes. The majority of the time it is the bassline that provides the driving force, often reinforcing the kick drum on the beat. In some systems, such as the NES, the triangle waveform channel can be pitched down at the start of the notes to give the impression of a deeper sound, further reinforcing the kick drum.

As just discussed the typical sound for a kick drum is one that provides the foundation to the track. As such they tend to be quite punchy, so it may be said to have a quick attack and quick decay with regards to their envelope. The majority of the time tom toms do have a similar envelope to kick drums. However extending the release of the envelope, which will be discussed in the next section, gives the tom a more open and sustained sound, as you would hear if you physically struck a tom tom in real life.

Kicks also tend to be low in pitch, so it can be said that the frequency content consists of low frequencies, or at least frequencies in the lower range. This is the main area where kick drums differ from toms, as tom toms have varying pitches depending on their size, or implied size when it comes to the digital realm. The larger the tom the lower its tone, the smaller the tom the higher its tone.

Understanding these two fundamentals are the building blocks for pretty much every percussive sound you will encounter. Once you have grasped the basics of these the world is your percussive oyster.

Envelope Shape:

If you are new to synthesis you may be wondering what an envelope it. Let’s clarify that in this case it definitely doesn’t transport pieces of paper from one location to another. When it comes to synthesis an envelope helps shape the sound. Shaping the overall outcome of any sound in a synthesiser is done via the amplitude (volume) envelope. So in the case of a kick drum the amplitude (volume) envelope will be the tool to shape the sound so that it has the right attack and decay.

As an example let’s take a look at how this can be done in an FM synth. My synth of choice at this stage is going to be Logic Studio’s EFM1. This synth is laid out in a very straight forward manner and helps with understanding the basics of FM synthesis. For the examples in this tutorial we aren’t actually going to implement any direct frequency modulation synthesis as these sounds can be created without any. However the sounds can be enhanced with frequency modulated synthesis and this will be demonstrated further down the line.

• Starting with a blank canvas let’s take a look at the aspects of an envelope. These are the attack, decay, sustain and release. In this example we are editing the amplitude (volume) envelope as this controls the overall shape of the sound. Notice the volume envelope on the bottom right hand corner of this synth. This is what we will be focusing on today.
• As a kick drum has a short sound that starts instantly you want a very fast attack, short decay, little or no sustain and a very short release. As can be seen from the image above the attack slider is very far down, pretty much at the bottom. This creates an instant start to the sound. The sound has a very slight decay which creates the punch to this sound, especially with the release being all of the way down. The sound clip below demonstrates what this sounds like.

• To get fatter, slightly longer sound you can extend the attack slightly, as in the image below. Extending the attack slightly removes that click at the start of the sound and instead gives it a rounded sound at the beginning. The decay can also be extending a tiny amount to let the kick sound play for long when the midi note or midi keyboard is played. An example of what it sounds like is below.

• Or to have a longer kick sound with less punch, much like an 808 style kick, you can extend the release to suit your taste. Extending the release will also give the tom tom sound, which will be noticed if the the sound is played higher pitched. The image below shows what the amplitude envelope will look like in these cases.

Harmonic Content:

Deciphering the harmonic content of a sound will allow you to select which waveform the sounds will consist of. Chiptunes typically consist of simple waveforms such as saw, square, triangle and sine waves. So when composing chiptune sounds you really want to keep to these simple waveforms. However the way FM synthesis works is by modulating one waveform with the frequency of another waveform. This creates very complex waveforms and the maths behind it can get very complex. So for the next few articles the EFM1 will my weapon of choice to explain basics of FM synthesis and how sounds can be created. For instance a future article will discuss how to create a short pitch bend at the start of drum sounds to further enhance them. As the maths can get very complicated with FM synthesis a lot of the time once you have the basics down and understand how it works it is best to refine sounds by ear.

If you listen carefully to kick drums and tom toms you will hear that they are quite plain in harmonic content. That is they don’t have the raspy sound of a saw wave, or the slightly raspy but more hollow sounding square wave. In my opinion they are best constructed from sine waves, which is the simplest waveform as it contains no harmonics aside from the root frequency. The sounds you hear above don’t involve any frequency modulation to effect their pitch or tone. So later articles will show how to incorporate frequency modulation into what is currently existing here to see how the sounds can be modified.

Joe Gilliver – BA Hons (Ocular Audio)

Composer | Producer | Sound Designer

www.ocularaudio.com