It determines how the sound changes in time by modifying some parameter, like volume or filter cutoff, but you can certainly also use it to change stuff like LFO speeds, distortion, how much FM you want or really anything in the world. If your synth/instrument supports that.
Let's say your envelope controls the volume of a synth, and the press of a key triggers the envelope (which is usually the case). An envelope typically has some certain parameters and this is what happens when you change it:
Delay - If set to 0, the sound will start playing immediately. If you set it higher, you won't hear anything for a moment (the moment will be longer the higher you set the "Delay" value). Not all envelopes have this parameter.
Attack - if set to 0, the sound will be at its loudest as soon as you hit the key. If you set it higher, the sound will fade in and hit the peak volume after some time. How long it takes for the sound to hit the peak volume depends on how high you set the attack value.
Decay - After the Attack "phase", if Decay is set to 0, the sound will immediately go to the volume determined by Sustain. If you set Decay higher, this will happen gradually. Decay determines how long it takes for the sound to go from peak volume to the volume determined by Sustain.
Sustain - After the Decay "phase", if Sustain is set to 0, the sound will gradually fade out and become silent while you're still pressing the key. If Sustain is set higher, the sound will be audible as long as you press the key. The Sustain value determines how loud the sound is after the Decay "phase".
Hold - Not very many envelopes have this. It determines how long the sound will stay at the Sustain level after the decay phase.
Release - Determines how long it takes for the sound to fade out after you've let go of the key. If you set it to 0, the sound will abruptly stop as soon as you let go. If you set it to it maximum, it might never fade out but stay at a constant volume forever or at least until you change the release value again.
If the envelope controls the amplitude/volume/level of an instrument, it's typically called an "Amp/Amplitude Envelope" and if it controls the cutoff value for a filter, it's typically called a "Filter Envelope". Some synths may have envelopes that can be assigned to any parameter, these will most likely just be called "Envelope" or "Mod Envelope".
At 3/19/11 12:36 PM, SineRider wrote:
You put a letter in them, seal em' up, then put a stamp and address and people get them in the mail
Funny