SB AWE32 Developer's Information Pack
PART IV MIDI NRPN Implementation
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87
Copyright
Creative Technology Ltd., 1994-1996
Version 3.00
example of a GM instrument that makes use of LFO1 to Filter Cutoff is instrument number 19, Rock
Organ.
LFO1 to Pitch (Vibrato)
As indicated in figure 1, LFO1’s output is routed to the oscillator, with the depth of oscillation
determined by LFO1 to Pitch. LFO1 to Pitch produces a periodic fluctuation in the pitch of the oscillator,
producing a vibrato effect. An example of a GM instrument that makes use of LFO1 to Pitch is instrument
number 57, Trumpet.
LFO2 to Pitch (Vibrato)
The LFO1 in the EMU8000 can simultaneously modulates pitch, volume and filter. LFO2, on the other
hand, modulates only the pitch, with the depth of modulation determined by LFO2 to Pitch. LFO2 to Pitch
produces a periodic fluctuation in the pitch of the oscillator, producing a vibrato effect. When this is
couple with LFO1 to Pitch, a complex vibrato effect can be achieved.
Volume Envelope
The character of a musical instrument is largely determined by it’s volume envelope, the way in which
the level of the sound changes with time. For example, percussive sounds usually starts suddenly and
then die away, whereas a bowed sound might take some time to start and then sustain at a more or less
fixed level.
A six-stage envelope made up the volume envelope of the EMU8000. The six stages are delay, attack,
hold, decay, sustain and release. The stages can be described as follows :
Delay
The time between when a key is played and when the attack phase begins
Attack
The time it takes to go from zero to the peak (full) level.
Hold
The time the envelope will stay at the peak level before starting the decay
phase.
Decay
The time it takes the envelope to go from the peak level to the sustain level.
Sustain
The level at which the envelope remains as long as a key is held down.
Release
The time it takes the envelope to fall to the zero level after the key is
released.
Using these six parameters can yield very realistic reproduction of the volume envelope characteristics
of many musical instruments.
Pitch and Filter Envelope
The pitch and filter envelope is similar to the volume envelope in that it has the same envelope stages.
The difference between them is that whereas the volume envelope contours the volume of the instrument
over time, the pitch and filter envelope contours the pitch and filter values of the instrument over time.
The pitch envelope is particularly useful in putting the finishing touches in simulating a natural
instrument. For example, some wind instruments tends to go slight sharp when they are first blown, and
this characteristics can be simulated by setting up a pitch envelope with a fairly fast attack and decay.
The filter envelope, on the other hand, is useful in creating synthetic sci-fi sound textures. An example of
a GM instrument that makes use of the filter envelope is instrument number 86, Pad 8 (Sweep).