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 () 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
KT with VIBRATO

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" 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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