From How and What to When and Why – Part 1

Congratulations! We now have enough knowledge to make a variety of sounds from Clearsynth!

Just to recap what we’ve learnt so far:

  1. We know how to use the two oscillators together, and mix them with varying volumes
  2. We know what filters are, and how to select different types of filters.
  3. We know about volume envelopes, and how to control them.

For someone starting out, these present a lot of options. In this tutorial, and the next, we’ll look at when to choose, say, a sine wave versus a saw wave, when to lowpass and when to highpass, what volume envelope to use etc.

Let’s start with Oscillators.

If you’ve been following along the tutorials, you’ve already heard the four different waveforms in isolation, and know what they sound like. Sine, saw, triangle and square, each have their characteristic ‘sound’. Why is that so? It’s all well and good to say that these waveforms look different. But what is the difference between these waves sound wise?

Remember, I told you before that any sound we hear is a mix of frequencies? Play your favorite record on a spectrum analyzer, and you’ll see a whole lot of frequencies jumping up the graph, from the lower frequencies of the kick drum, to the higher frequencies of the hihat. Even the common sounds you hear every day, like the slamming of a car door, the bark of a dog, or the noise of a vacuum cleaner, are all made up of a mixture of frequencies.

Ever wondered what a single frequency will sound like? Select the sine preset on Clearsynth (or choose a single sine waveform with everything else off) and play a note. That’s how it sounds like! 🙂

The sine wave

A sine wave is called as a fundamental waveform because of this. Explaining about these waveforms involves a whole lot of scientific formulae, swinging pendulums and French mathematicians, so we won’t get into all that. Think of a sine wave as a basic single frequency waveform (also called a harmonic). It’s the ‘atom’ of the sound world: there is no waveform more basic than a sine wave. This waveform is sometimes called as a “pure tone”.

This makes a sine wave useful for generating smooth tones, and sub-bass sounds. But sine waves are usually not used in Subtractive synthesis as much as the other waveforms. The reason is simple. In Subtractive synthesis, we take waveforms from which we subtract frequencies from to get the resultant sound. If the source waveform is a sine wave, then it’s a single frequency, and subtracting the only frequency that it has will end up in silence!

Generally, sine waves are used along with another waveform to add the sub bass, or smoothness to the sound.

The sawtooth wave

If sine wave has only one frequency, the saw tooth wave, however, has all the possible frequencies. So, while the sine wave sounds simple and smooth, the saw wave sounds buzzy and rich.

Note that I said the saw wave has all the possible frequencies. What do I mean by that? For any sound to have a pitch, there has to be a fundamental frequency, and other frequencies that are a multiple of a fundamental frequency. Saw waves have every multiple of the fundamental frequency: that is, the fundamental frequency + 2 times the fundamental frequency + 3 times the fundamental frequency… and so on. All these frequencies are at different amplitudes (a ratio of the frequency multiple).

Yeah… I know I said I won’t get into the math of it all. It’s perfectly okay if you don’t understand the math. What’s more important is to get the feel of the sound. Just realize that a saw wave has the most harmonics among the four waveforms we’ve seen. This results in the buzzy sound. Which is what makes it ideal for subtractive synthesis, as it is a rich source of frequencies, and there is so much to subtract from.

Because of this richness, saw waves are an ideal starting point to synthesize brass instruments like trumpets, and string instruments.

Note: It’s not a random choice why I asked you to choose the saw waveform when I was explaining filters. Try the same filter exercises on a sine wave and hear the result. Since there is only one frequency there, you cannot hear the effect of a gradual filter cut. The sound is either on or off.

The square wave

This wave has only the odd harmonics. The even harmonics are not present at all. So, it’s slightly duller than the saw, but it still has more richness compared to a sine wave. Square waves can be used for brass-instrument-like sound too, but for those which have slightly less character (like the clarinet or sax, for instance).

The triangle wave

This wave too has odd harmonics, but the volume of the harmonics dampens out quickly. This makes it duller than a square wave. Triangle waves can also be used along with other waveforms to add extra character to the sound.

I know this is a whole of theory for a single tutorial. But trust me, this is really important. If you’ve put the effort and read this through, then go and listen to the waveforms now. It’ll all fall into place! Not only will you have a mental picture of why the different waveforms sound different, you’ll also instinctively know what waveform to use when you are looking for a particular sound.

On to part 2. The next tutorial won’t have this much theory, I promise. All the hard work is over. 🙂


4 Responses to “From How and What to When and Why – Part 1”

  1. January 12, 2010 at 11:07 pm

    really good information !!
    thanks so much keep doing what u doing !!!

  2. 2 Masr
    February 3, 2010 at 7:00 pm

    Great stuff, really. As a beginner in synths I am really excited about this information. Thanks very much.

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