Casio CZ Envelopes—About
What Are Envelopes
“Envelope” is a funny word to use because it’s not something you mail a letter in. In the context of synthesizers or audio editing, an envelope is the name for a change that is applied to a sound over a period of time.
Let’s say you have a continuous droning sound. You could apply an envelope to it that makes the sound get louder for the first second, quieter for the second second, steady for the third second, and fade to nothing in the fourth second. That would be a basic amplitude envelope, since it is changing the amplitude of the sound.
Casio’s CZ Envelopes
Back when the Casio CZ line were being made, a lot of synthesizers used basic ADSR envelopes. ADSR stands for Attack, Decay, Sustain, and Release. That is a way of modeling sound that goes back to the first electronic instruments.
Casio created the CZ line with more than just ADSR envelopes for the sounds. They created eight stage envelopes that could go up or down in whatever order you want. The sustain can appear at any point in the envelope. You can end the envelope early if you don't want to use all eight stages.
Having eight stages for each envelope means there are a lot more sonic possibilities than a synthesizer that has only three or four stages.
There are three main sound sections on a Casio CZ synthesizer: Pitch (DCO), Wave (DCW), and Amplitude (DCA). Each of these three sections has its own eight stage envelope that is independent. That means the pitch can change in complex ways, while the waveform is changing in different complex ways, while the amplitude is changing on still more complex ways.
In addition to the complexity already mentioned, there are two independent lines of sound. Those two lines are independently complex and can be layered to create even more possibilities.
The point is, the envelopes create a lot of possibilities. Other synthesizers have a lot of possibilities too, so I don't want to overstate what the Casio CZ offer.
Rate And Level
The Casio CZ envelopes function by specifying the rate and level.
Rate and level
Level is easiest to explain. Each effect that is being controlled can go from zero effect, to full effect. When you specify the level, you specify how much effect you want to dial in. Higher numbers means more of whatever property is being controlled.
Rate is how quickly you go from one level to the next. If the rate is a small number, it will take longer to get to the next level. If the rate is a large number, the sound will go to the next level quickly.
Why Rate And Level?
You may wonder, as I did, why Casio chose to use a “rate and level” model. If you know the rate and the level, you can calculate the time. And if you know the time and the level, you can calculate the rate. So why not use a “time and level” model for these settings?
One reason: using the “rate and level” model, the synthesizer never has to know when something happened. There is a clock running, as the sound is created, that provides the time element for the sounds. But the program doesn’t try to know or calculate the time when anything happens.
Using a “time and level” model would require multi-faceted calculations to get anything done. Thanks to Bill Harrison for bringing this up.