64 |
Nord Wave User Manual v1.1
Resonance
resonance in a filter is created by increasing the routing of
the output from the filter to its own input. the amount of
feedback is then controlled with a resonance function on
the front panel of the instrument.
When you apply resonance, the frequencies just around
the cutoff point of the filter will be emphasized (louder). as
you increase the resonance further and further, the filter
will start to behave more an more like a bandpass filter,
where only the frequencies around the cutoff point are let
through. the filter will start to “ring”, which means it almost
sounds like it is adding frequencies to the sound. If the
resonance is then raised even further (on some synthe-
sizers) the filter will start to self-oscillate, that is produce
sound of its own, just like an oscillator.
high resonance values are also visible in the waveform.
they appear as a “superimposed” waveform with a frequen-
cy equivalent to the filter’s cutoff frequency.
If you add resonance to a sound and then vary the Cutoff
frequency (for example with an envelope) you will get a
very typical synthesizer sound.
The Amplifier
an amplifier is most often used at the final stage of a
synth signal chain, to control volume. By modulating the
amplifier with an envelope, the sound can be given its
basic “shape”. In fact, the “volume shape” is one of the most
important factors to how we identify the sound. By setting
up a proper volume envelope you can make a sound “soft”,
“hard”, “plucked” “static” etc.
Envelopes
ADSR-envelope
Envelopes are used to modulate pitch, amplitude, filter
cutoff and other parameters in a sound. this is used to give
the sound a varying character from the moment the key is
pressed to the moment it is released.
the classic synthesizer envelope has four parameters,
attack, decay, Sustain and release, and is therefore often
referred to as an “adSr-envelope”.
When you press a key, the envelope is triggered. this
means is starts from zero and rises to the maximum level.
how long this should take, depends on the attack setting.
If the attack time is set to “0”, the envelope will instantly
reach full level. If the attack time is higher it will take lon-
ger.
If you for example have an envelope controlling volume,
raising the attack will give the sound a “softer” character. If
you have the envelope routed to the filter, it might give the
sound a “wah” type of start.
after the envelope has reached full level, it starts to fall
back again. how long this should take, is set with the
decay parameter.
the level of the envelope does not necessarily have to
fall all the way back to zero level at the end of the decay.
Instead, the adSr-envelope has a Sustain setting used to
determine the level the envelope should rest at, after the
decay.
If you for example want to create a flute sound, you would
have a fairly high Sustain setting on your amplifier en-
velope, since a flute tone basically stays at a steady level
for as long as you blow it. on the other hand, for a piano
sound, you would want a Sustain level of “0”, since a piano
sound decays to silence if you hold the key long enough.
Please note that the Sustain parameter represents a level,
but all other envelope parameters represent times.
as described above, the envelope stays at the Sustain level
until the key is released. It then falls back to zero level.
the time it should take for this to happen is set with the
release parameter, which works just as the decay, but it is
not applied until you lift your finger off the keys.
If you set Sustain to full level, the decay setting is of
•
no importance since the volume of the sound is never
lowered:
If you set Sustain to 0, the sound will become silent after
•
the decay phase is finished. With short attacks moder-
ate decay times, this can be used to simulate the be-
havior of a plucked string instrument (guitar, piano etc)
where the sound always decays to silence after a while:
If you release a key before the envelope has reach its
•
sustain, it will immediately “jump” to the release.
the effect of this can be studied in the illustration below:
often envelope amounts can be made to vary with how
hard you play the keys. this is used to make a sound vary
