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OM-Chant 2.0 User Manual
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Modulating Effects

Different tools in OM allow for the generation of continuous controllers suitable for the specification of parameters in OM-Chant events. The outputs of the following generators are BPFs which can be connected to the OM-Chant just as described in the previous sections.

PARAM-PROCESS (Vibrato, Jitter)

The function PARAM-PROCESS modulates an input parameter (<initval> = constant value or BPF) with a combination of vibrato (sinusoidal modulation) and/or jitter (random perturbation) effects (<function>). Both jitter and vibrato are determined by a frequency <freq> and amplitude <amp>. They are applied to generate a controller of length <duration>, modulating <initval> at rate <kt> (optional), either by addition or multiplication (<op>).

Simple Jitter, constant value:

The followinf example generates a BPF updated at a given frequency (freq) to randomly perturb the initial value (<initval>) by a given factor (amp) during 3 seconds.

Multiple Jitters

Multiple values can be given for the frequencies and/or amplitudes of the jitter effect, producing a combination of the corresponding modulations.

Jitter control rate

<kt> is not used with Jitter effects. The resolution of depends on the Jitter frequency[-ies].

Jitter on BPFs

Applied on BPFs, the jitter perturbates the curves at each time determined by the frequencies.

The following example also illustrates the difference between modulating by addition (‘a' = addition of initial value * amp to the initial value) and by multiplication (‘m' = multiplication of the initial value by amp).

Duration with BPFs

When <initial-value> is a BPF and <duration> is NIL, the original BPF duration is preserved. Otherwise the effect(s) apply during the specified duration.

All same principles apply with the VIBRATO effect

With the VIBRATO effect the control rate <kt> has to be specified, otherwise OM will automatically choose one corresponding to the smallest possible value to avoid spectral aliasing.

Dynamic/Continuous Effects

Effects themselves can have their parameters (freq, amp) varying over time. In this case, the frequency and amplitudes must be specified as BPFs [time (sec.) / value]. In the next examples the frequencies raise while the amplitudes of the effects decrease.

Effects combinations

It is possible to combine JITTER and VIBRATO on a same PARAM-PROCESS:

Application to Chant synthesis
Tutorial patch : "apply-vibrato"
Tutorial patch : "apply-vibrato"

One of the main use of PARAM-PROCESS with VIBRATO is for the modulation of the frequency in CH-F0 events:

The tutorial patch "example" monster illustrates the use of jitter and modulations to the parameters of the FOF generators.

Pulse train

In certain cases it will be useful to generate a pulse train as a continuous specification for a given Chant parameter. The function PULSE-TRAIN provides a great flexibility to generate such controller:

Use d to see the PULSE-TRAIN reference page and get a complete description of the parameters.

Application to Chant synthesis

In this example we use PULSE-TRAIN to generate the amplitude of the noise in the CH-NOISE event with Chant synthesis patch #4 (NOISE+FILTER).

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