Sound Illusions - 1. This first audio illusion is an example of a tone series, called sheppard tones after the discoverer, that has the quality of going - well, up, down or just plain nowhere. Just roll the mouse over any pad to hear a tone - and follow the instructions written below. The the relationship of the pitches of the light green and blue pads seems to change depending on which way you step around the circle...
Sound Illusions - 2. This second illusion is similar in some ways. Roll the mouse over the left end of the keyboard to hear a chord played (it's rather dissonant, but that's part of the illusion). Move the mouse towards the right end of the keyboard and the same chord will be played exactly one octave higher. There is no need to click the mouse. Keep trying the two chords. There is no cheating going on - athe two chords are identical, just played an octave apart. Does the sound go up or down? If you are intrigued by this effect, our Digital Audio class will provide some explanations and help you to discover just how sound works and how we hear it...
This next one is not an illusion, just the tones of the C major scale. You can recognise the different intervals, right? When you listen to or play music, it is important (and convenient) to be able to identify the "distances" between notes of the scale. Click on each note to hear it play...
Sound Design - Synthesis (as opposed to field or instrument recording) is central to electronic music. Using either an additive bank of oscillators, samples and filters or FM gives an opportunity to make sounds that are real-time controllable and as a result are often better able to be integrated into compositions. Field recording offers a great opportunity for realism and identity, but sometimes post-recorded control of the sound is difficult - though digital audio tools are becoming more and more powerful. Here are some examples:
Oscillator banks allows control over individual harmonics/overtones with the possibility of controlling the development of a timbre over time in an interesting way. These three sounds are all made by varying the properties of a collection of sine waves
Sampling and resampling allows layers to be piled up to give rich textural effects. When sampling is used to re-create familiar instruments there is a strong sense of identity (getting the timbral behavior right can be a little more difficult. Here are some simple layered sounds, easily done using a standard sampler, or a wave table synth and a sequencer...
FM is a genuinely parametric form of synthesis that allows instruments to be built with great detail. The nature of FM makes it easy to make sounds that are very responsive to dynamics and pitch behavior. Though the "identity" of FM sounds is less accurate than sampling or physical modelling, the behavior of notes can be very realistic, lending a special responsiveness that players of FM synths usually appreciate...
Field Recording can be like a microscope on the audio landscape. It's great fun to go out and record animals, rain, wind, traffic and so on. This sound is not really "natural" - its a rainstick made for a daughters school project - but you can really hear those beads trickling down the cardboard tube...
Having written a book on FM Synthesis together with it's inventor, Dr
John Chowning, I feel obliged to share... The basic building block of FM
is the Operator – an element which typically generates a simple sine
wave, which is a simple and mellow tone. When a second operator is
allowed to “modulate” the first, harmonics are generated making the
sound brighter. FM synths usually have a group of “operators” at their
core, all connected together in some way, called an algorithm or matrix.
Before you even begin to explore how FM really works, it is helpful to
be able to “read” an algorithm or matrix. A good way to get a handle on
this, is to break the model down into chunks that contribute elements of
audio to a voice, and simply turn them up or down. To do this, you need
to understand how the sound is built up in the algorithm, and how sound
“flows” through it.
In the above representation, it is
quite reasonable to think of sound flowing from left to right out of
each operator, through the connecting pipes, then brightening the output
of every operator that it flows through, until it arrives at the output
on the far right. The only way for sound to come out of the system is
“through” an operator. In the case of this configuration, or Algorithm,
it can be described like this…
- Operator 4 outputs a sound - it is connected directly to the output. For the algorithm shown, all sound flows through this operator therefore its output level and envelope become “master” controls.
Here are two other algorithms. Spend a moment to think about the sound flow in each one, ask yourself how each operator might affect the sound. For example, what happens in each case if Operator 3 is turned off? In the case of Algorithm 4 on the right, operator 4 would sound but without any modification at all; for Algorithm 5, operator pair 3 & 2 would become silent, but operator pair 4 & 1 would continue to sound, the sound of operator 4 still being modified by operator 1.