<BGSOUND SRC="jazz1.au">
Envelope Generators: The shapers of sound.
In addition to sound having a pitch and a wave form sounds have shape and change over time. Envelope generators provide the means for shaping sound over time. Sounds have a birth, a life, and a death.
The birth portion of the sound is called the "attack and initial decay". This portion gives the sound much of it's characteristic. The ear uses the attack portion it know what a sound is. This initial portion is probably the most important because when we were evolving we needed to know if that sound was food, or something that wanted to make us food - so a quick ID of the sound was essential. For some sounds, mainly percussion, this is all there is. Velocity (how fast(hard)) and pitch (key number) can be used to change the length of the attack portion)
The life of the sound is the sustain; as long a key is held down the sound stays more or less the same. On the SQ-80 you can use the "second decay" as a slowly fading sustain (that would be most realistic on a plucked string) or don't use it and maintain a level sustain using the sustain level. Organs, winds, bowed strings have a more or less steady sustain. Other modulators can be used to add "life" to this generally steady sustain (See LFOs and also Other Modulators). The sustain starts after the attack/decay portion of the envelope completes, and remains as long as the key is held down (or held using the pedal).
The death of the sound is the release. After the key is released the sound starts to fade away,the sound starts to die. The way a sound dies is determined by the Release portion of the envelope generator. The SQ-80 has a second release that function somewhat like a "reverb" ... adding a bit of depth to the sound.
The envelope generators, and there are four on the SQ-80, can be used to modify any number of things. There are three properties of the sound that typically are controlled by an envelope: Amplitude or loudness by modulating one for the four Digital Controlled Amplifiers, Timber or tone "color" by modulating the Digital Controlled Filter, and pitch by modulating the DCO's.
The envelopes generally have a level and a time to get to that level. When the key is released the envelopes go right to the release stage and start on the way to zero. The table shows how long it takes to get to each level, assuming the values for TK=0 and T1V=0, and the key is held down long enough to run a complete "cycle". Non zero values of TK and T1V tend to make the times shown shorter. There are parameters on the modes page (VC, ENV, CYC) that can change the way envelopes function as well.
Each of the 4 envelope pages (ENV1 - ENV4) have the following controls:
L1 - Level 1. This is the MAXIMUM level that the envelope will reach at the end of time 1. Envelopes usually start at zero and head towards the value set by L1. MODES - ENV (and VC) can change this. Range: -63 to +63.
L2 - Level 2. The MAXIMUM level at the end of Time 2. TK can reduce the maximum levels of L1, L2, and L3. Range -63 to +63.
L3 - Level 3. The maximum level at the end of T3. -63 to +63 again is the value.
LV - Level control via Velocity. LV subtracts from the maximum values of L1, L2, and L3. The larger the value the larger the subtraction. In general a large value of LV will give you a larger range that the initial speed or hardness you hit a key will affect the envelope. There are two ranges: 00L to 63L and 00X to 63X. The "L" ranges are for linear response and generally track along with your key strikes. the "X" ranges are for Exponential response and can be use to "split" the envelopes in to a hard response and a soft response. Used with the DCA's for instance you can use the X values to have one attack if you hit the keys softly, and a different one for hard hits.
T1V - Time 1 control Velocity. The HIGHER this value is and HARDER (faster) a key is struck the SHORTER time it will take to reach L1. This has no effect of the value is 0 or T1=0.
T1 - Time 1. The MAXIMUM time to reach level 1. Generally this is the attack time. However if the VALUE of L1 = 0 this can be used to DELAY the start of a sound - useful to apply a sustain after waiting for an attack for instance. Range: 0 to 63.
T2 - Time 2. The time to reach Level 2 from Level 1. By setting T1 to 0, all levels and values of L (except L1), and T (except T2) to zero you can use the value of L1, and the Time of T2 to "slide" to the pitch of a note from some known value. Value: 0 to 63.
T3 - Time 3. The time to reach Level 2 to Level 3. The envelope will, in most cases stay at the L3 value until the key is released. If CYC=ON in the MODES page the sustain will be bypassed just as if the key was released at the exact moment level 3 is reached if the key is held down. If the key is released the envelope will start the T4 processing as normal.
T4 - Time 4. The time to go from the current value (usually Level 3) to zero. Note: The values of "T" are a FIXED amount of time [See the table], not a rate. Unless modified by TK or T1V the times to reach a value will remain the same. If L3 has not been reached then releasing a key will take the same amount to time to get to zero as if L3 had been reached. When you release a key it takes L4 time to get to zero. L4 has two ranges 00 to 63 and 00R to 63R. The "R" ranges after dropping to a low value, do not continue at the same rate to 0, but instead fade slower to zero at a fixed low rate. The "R" ranges simulate a "reverb" and add "space" to the sound. While clean, and useful in it's day the "R" values have a tendency to get stepped on as the SQ-80 has only 8 voices. Use the "R" values with care. An inexpensive reverb unit is a good addition to the SQ-80. On the other hand the "R" values allow some voices to have "space" and others not.
Return to the SQ-80 main page
page created by:
webmaster@dulcimoo.com
Changes last made on:
Tue 12 Dec 2003
©2002-2003 dulcimoo.com, 1987-1989 Ensoniq (Now Creative Labs)