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class:: Env
summary:: Specification for a segmented envelope
related:: Classes/EnvGen, Classes/IEnvGen, Classes/Pseg
categories:: Control, Envelopes

description::
An Env is a specification for a segmented envelope. Envs can be used both server-side, by an link::Classes/EnvGen:: or an link::Classes/IEnvGen:: within a link::Classes/SynthDef::, and clientside, with methods such as link::#-at:: and link::#-asStream::, below.

An Env can have any number of segments which can stop at a particular value or loop several segments when sustaining. It can have several shapes for its segments.

code::
Env.new([0, 1, 0.9, 0], [0.1, 0.5, 1],[-5, 0, -5]).plot;
::

The envelope is conceived as a sequence of emphasis::nodes:: (not to be confused with a synthesis-Node) each of which has three parameters: a target level, a time duration from the previous node, and a shape. The three parameters for each node are kept in separate arrays as explained below.

note::
In some situations we deal with control points or breakpoints. If these control points have associated x positions (say in an envelope GUI, see link::Classes/EnvelopeView::) they must be converted to time differences between points to be used as nodes in a Env object. The methods link::#*xyc:: and link::#*pairs:: can be used to specify an envelope in terms of points.
::

code::
// an envelope in a synth
(
{
        var env = Env([0, 1, 0.5, 1, 0], [0.01, 0.5, 0.02, 0.5]);
        SinOsc.ar(470) * EnvGen.kr(env, doneAction: 2)
}.play
)
// an envelope to control a parameter in a pattern
(
Pbind(
        \note,  Env([0, 12, 6, 13, 0], [1, 5, 2, 10]),
        \dur, 0.1
).play
)
::

ClassMethods::

private::initClass

method::new
Create a new envelope specification.

argument::levels
an array of levels. The first level is the initial value of the envelope. When the envelope is used with an EnvGen, levels can be any UGen (new level values are updated only when the envelope has reached that point).
When the array of levels contains itself an array, the envelope returns a multichannel output (for a discussion, see link::#multichannel expansion::)

argument::times
an array of durations of segments in seconds. There should be one fewer duration than there are levels, but if shorter, the array is extended by wrapping around the given values.

argument::curve
a link::Classes/Symbol::, link::Classes/Float::, or an link::Classes/Array:: of those. Determines the shape of the envelope segments.

The possible values are:
table::
## code::\step:: || || flat segments
## code::\linear:: || code::\lin:: || linear segments, the default
## code::\exponential:: || code::\exp:: || natural exponential growth and decay. In this case, the levels must all be nonzero and have the same sign.
## code::\sine:: || code::\sin:: || sinusoidal S shaped segments.
## code::\welch:: || code::\wel:: || sinusoidal segments shaped like the sides of a Welch window.
## code::\squared::  || code::\sqr:: || squared segment
## code::\cubed:: || code::\cub:: || cubed segment
## a link::Classes/Float:: || || a curvature value for all segments. 0 means linear, positive and negative numbers curve the segment up and down.
## an link::Classes/Array:: of symbols or floats || || curvature values for each segment.
::

argument::releaseNode
an link::Classes/Integer:: or nil. The envelope will sustain at the release node until released.

argument::loopNode
an link::Classes/Integer:: or nil. If not nil the output will loop through those nodes startign at the loop node to the node immediately preceeding the release node, before back to the loop node, and so on. Note that the envelope only transitions to the release node when released. Examples are below. The loop is escaped when a gate signal is sent, when the output transitions to the release node, as described below.

argument::offset
an offset to all time values (only applies in link::Classes/IEnvGen::).

discussion::
code::
(
{
        var env = Env([0.0, 0.5, 0.0, 1.0, 0.9, 0.0], [0.05, 0.1, 0.01, 1.0, 1.5], -4);
        var envgen = EnvGen.ar(env, doneAction: 2);
        SinOsc.ar(
                envgen * 1000 + 440
        ) * envgen * 0.1
}.play
);

::



method::newClear
Creates a new envelope specification with strong::numSegments:: for filling in later.
discussion::
This can be useful when passing Env parameters as args to a link::Classes/Synth::. Note that the maximum number of segments is fixed and cannot be changed once embedded in a link::Classes/SynthDef::. Trying to set an Env with more segments than then this may result in other args being unexpectedly set. See link::#newClear:: example below.

subsection::Standard Shape Envelope Creation Methods
The following class methods create some frequently used envelope shapes based on supplied durations.

method::linen
Creates a new envelope specification which has a trapezoidal shape.

argument::attackTime
the duration of the attack portion.

argument::sustainTime
the duration of the sustain portion.

argument::releaseTime
the duration of the release portion.

argument::level
the level of the sustain portion.

argument::curve
the curvature of the envelope.

discussion::
code::

Env.linen(0.1, 0.2, 0.1, 0.6).test.plot;
Env.linen(1, 2, 3, 0.6).test.plot;
Env.linen(1, 2, 3, 0.6, \sine).test.plot;
Env.linen(1, 2, 3, 0.6, \welch).test.plot;
Env.linen(1, 2, 3, 0.6, -3).test.plot;
Env.linen(1, 2, 3, 0.6, -3).test.plot;
Env.linen(1, 2, 3, 0.6, [[\sine, \welch, \lin, \exp]]).plot;
::

method::triangle
Creates a new envelope specification which has a triangle shape.

argument::dur
the duration of the envelope.

argument::level
the peak level of the envelope.

discussion::
code::
Env.triangle(1, 1).test.plot;
::

method::sine
Creates a new envelope specification which has a hanning window shape.

argument::dur
the duration of the envelope.

argument::level
the peak level of the envelope.

discussion::
code::
Env.sine(1, 1).test.plot;
::

method::perc
Creates a new envelope specification which (usually) has a percussive shape.

argument::attackTime
the duration of the attack portion.

argument::releaseTime
the duration of the release portion.

argument::level
the peak level of the envelope.

argument::curve
the curvature of the envelope.

discussion::
code::
Env.perc(0.05, 1, 1, -4).test.plot;
Env.perc(0.001, 1, 1, -4).test.plot;    // sharper attack
Env.perc(0.001, 1, 1, -8).test.plot;    // change curvature
Env.perc(1, 0.01, 1, 4).test.plot;      // reverse envelope
::


method::pairs
Creates a new envelope specification from coordinates / control points

argument::pairs
an array of pairs [[time, level], ...]

argument::curve
the curvature of the envelope.

discussion::
code::
Env.pairs([[0, 1], [2.1, 0.5],  [3, 1.4]], \exp).plot;
Env.pairs([[0, 1], [3, 1.4], [2.1, 0.5], [3, 4]], \exp).plot; // pairs are sorted according to time
Env.pairs({ { 1.0.rand } ! 2 } ! 16, \exp).plot;
::


method::xyc
Creates a new envelope specification from coordinates / control points with curvature.

argument::xyc
an array of triplets [[time, level, curve], ...]

discussion::
code::
Env.xyc([[0, 1, \sin], [2.1, 0.5, \lin],  [3, 1.4, \lin]]).plot;
Env.xyc([[2.1, 0.5, \lin], [0, 1, \sin], [3, 1.4, \lin]]).plot; // pairs are sorted according to time
Env.xyc({ [1.0.rand, 10.0.rand, -4.rand2] } ! 16, \exp).plot;
::


subsection::Sustained Envelope Creation Methods
The following methods create some frequently used envelope shapes which have a sustain segment. They are typically used in SynthDefs in situations where at the time of starting the synth it is not known when it will end. Typical cases are external interfaces, midi input, or quickly varying TempoClock.

code::
(
SynthDef(\env_help, { |out, gate = 1, amp = 0.1, release = 0.1|
        var env = Env.adsr(0.02, release, amp);
        var gen = EnvGen.kr(env, gate, doneAction: 2);
        Out.ar(out, PinkNoise.ar(1 ! 2) * gen)
}).add
);

a = Synth(\env_help);
b = Synth(\env_help, [\release, 2]);
a.set(\gate, 0); // alternatively, you can write a.release;
b.set(\gate, 0);
::



method::adsr
Creates a new envelope specification which is shaped like traditional analog attack-decay-sustain-release (adsr) envelopes.

argument::attackTime
the duration of the attack portion.

argument::decayTime
the duration of the decay portion.

argument::sustainLevel
the level of the sustain portion as a ratio of the peak level.

argument::releaseTime
the duration of the release portion.

argument::peakLevel
the peak level of the envelope.

argument::curve
the curvature of the envelope.

argument::bias
offset

discussion::
code::
Env.adsr(0.02, 0.2, 0.25, 1, 1, -4).test(2).plot;
Env.adsr(0.001, 0.2, 0.25, 1, 1, -4).test(2).plot;
Env.adsr(0.001, 0.2, 0.25, 1, 1, -4).test(0.45).plot;   // release after 0.45 sec
::

method::dadsr
As link::#*adsr:: above, but with its onset delayed by strong::delayTime:: in seconds. The default delay is 0.1.

method::asr
Creates a new envelope specification which is shaped like traditional analog attack-sustain-release (asr) envelopes.

argument::attackTime
the duration of the attack portion.

argument::sustainLevel
the level of the sustain portion as a ratio of the peak level.

argument::releaseTime
the duration of the release portion.

argument::curve
the curvature of the envelope.

discussion::
code::
Env.asr(0.02, 0.5, 1, -4).test(2).plot;
Env.asr(0.001, 0.5, 1, -4).test(2).plot; // sharper attack
Env.asr(0.02, 0.5, 1, 'linear').test(2).plot; // linear segments
::


method::cutoff
Creates a new envelope specification which has no attack segment. It simply sustains at the peak level until released. Useful if you only need a fadeout, and more versatile than link::Classes/Line::.

argument::releaseTime
the duration of the release portion.

argument::level
the peak level of the envelope.

argument::curve
the curvature of the envelope.

discussion::
code::
Env.cutoff(1, 1).test(2).plot;
Env.cutoff(1, 1, 4).test(2).plot;
Env.cutoff(1, 1, \sine).test(2).plot;
::

method::circle
Creates a new envelope specification which cycles through its values. For making a given envelope cyclic, you can use the instance method link::#-circle::

argument::levels
The levels through which the envelope passes.

argument::times
The time between subsequent points in the envelope, which may be a single value (number), or an array of them. If too short, the array is extended. In difference to the *new method, the size of the times array is the same as that of the levels, because it includes the loop time.

argument::curve
The curvature of the envelope, which may be a single value (number or symbol), or an array of them.  If too short, the array is extended. In difference to the *new method, the size of the curve array is the same as that of the levels, because it includes the loop time.


discussion::
code::
{ SinOsc.ar(EnvGen.kr(Env.circle([0, 1, 0], [0.01, 0.5, 0.2])) * 440 + 200) * 0.2 }.play;
{ SinOsc.ar(EnvGen.kr(Env.circle([0, 1, 0, 2, 0, 1, 0], [0.01, 0.3])) * 440 + 200) * 0.2 }.play;
{ SinOsc.ar(EnvGen.kr(Env.circle([0, 1, 0, (2..4), 0, (1..3), 0], [0.01, 0.3])) * 440 + 200).sum * 0.2 }.play; // multichannel expanded levels
::



subsection::Multichannel expansion
If one of the values within either levels, times, or curves is itself an array, the envelope expands to multiple channels wherever appropriate. This means that when such an envelope is passed to an EnvGen, this EnvGen will expand, and when the envelope is queried via the methods link::#-at:: or link::#-asSignal::, it will return an array of values.

code::
(
{
        var env = Env([0.0, 0.5, 0.0, [1.0, 1.25, 1.5], 0.9, 0.0], [0.05, 0.1, 0.01, 1.0, 1.5], -4);
        var envgen = EnvGen.ar(env, doneAction: 2);
        SinOsc.ar(
                envgen * 1000 + 440
        ) * envgen * 0.1
}.play
);

(
{
        var env = Env([1, [1, 2, 3], 0.5, 0.5, [3, 2, 1], 2], [1, 1, 0.5, 1], [[\exp, \sin]]);
        env.plot;
        Splay.ar(SinOsc.ar(EnvGen.kr(env) * 400 + 600)) * 0.1 
}.play;
);


(
{
        var levels = (1..30);
        var env = Env([1, levels, 0.5, levels / 2.5, 2], [1, 0.15, 1, 0.25, 0.1], \exp);
        Splay.ar(SinOsc.ar(EnvGen.kr(env) * 400 + 600)) * 0.1 
}.play;
);


// accessing the envlope by indexing

e = Env([1, [1, 2, 3], 1], [1, 1], \exp);
e.at(0.5);
e.at(1.8);
e.at(2);

e = Env([1, 1, 1], [1, [1, 2, 3]], \exp);
e.at(0.5);
e.at(2);


// multichannel levels

Env([0.1, 1, 0.1], [1, [1, 2, 3]], \exp).plot;
Env([0.1, 1, 0.1], [1, [1, 2, 3]], [\lin, [\lin, \exp, \sin]]).plot;

Env([1, 1, 0.5, 3, 2], [1, 0.5, 1, 0.25], \exp).plot;
Env([0, 1, 0, 2, 0] * [[1, 2, 3]], [1, 0.5, 1, 0.25], \lin).plot;


// multichannel curves

Env([0.01, 5, 1, 0.5] + 1, [1, 0.5, 1, 0.25], [[\lin, \sqr]]).plot;

Env([0.01, 5, 1, 0.5, 0.001] + 1, [1, 0.5, 1, 0.25, 1], [[\lin, \cub, \sin, \cubed, \welch, \step, \exp]]).plot(bounds: Rect(30, 100, 500, 700));

Env([0.01, 5, 1, 0.5, 0.001] + 1, [1, 0.5, 1, 0.25, 1], [(-4..4)]).plot(bounds: Rect(30, 100, 500, 700));
Env([0.01, 5, 1, 0.5] + 1, [1, 0.5, 1, 0.25], [(-4..4)]).plot(bounds: Rect(30, 100, 500, 700));


Env([[0, 0.01], 1, 0], [0.5, 0.5], [[\lin, \exp], \step]).plot;
Env([[0, 0.01], 1, [0, 0.01]], [0.5, 1], [[\lin, \exp]]).plot;

// multichannel times

Env([[2, 1], 0], [[1, 2]], \lin).plot;
Env([0, 1], [1/(1..5)], [(-4..4)]).plot(bounds: Rect(30, 100, 300, 700));
Env([0, 1], [1/(1..5)], \lin).plot(bounds: Rect(30, 100, 300, 700));


// mixed expansions

Env([1, [ 1, 2, 3, 4, 5 ], 0.5, [3, 2, 1], 2], [1, 0.5, 1, 0.25], [[\exp, \lin]]).plot;
Env([1, [ 1, 2, 3, 4, 5 ], 0.5, 4, 2], [1, 0.5, 1, 0.25], \exp).plot;


// expanding control point envelopes

Env.xyc([[2, 0.5, [\lin, \exp]], [0, 1, \lin], [3, 1.4, \lin]]).plot;
Env.xyc({ [1.0.rand, 1.0.rand, {[\lin, \exp, \step].choose} ! 3] } ! 8).plot

Env.xyc([[[2.0, 2.3], 0.5, \lin], [0, 1, \lin], [3, 1.4, \lin]]).plot; // multiple times


::

InstanceMethods::

private::prAsArray


method::ar, kr
Instead of using an link::Classes/EnvGen:: inside a UGen graph, this message does the same implicitly for convenience. Its argument order corresponds to the most common arguments.

argument::doneAction

An integer representing an action to be executed when the env is
finished playing. This can be used to free the enclosing synth,
etc. See link::Reference/UGen-doneActions::  for more detail.

argument::gate

This triggers the envelope and holds it open while > 0. If the
Env is fixed-length (e.g. Env.linen, Env.perc), the gate argument
is used as a simple trigger. If it is an sustaining envelope
(e.g. Env.adsr, Env.asr), the envelope is held open until the
gate becomes 0, at which point is released.

If strong::gate:: < 0, force release with time code:: -1.0 - gate ::, see link::#forced_release:: below.


argument::timeScale

Scales the durations of the segments.

discussion::
code::
{ Blip.ar(50, 200, Env.perc(1, 0.1, 0.2).kr(2)) }.play;
(
{
        Blip.ar(
                Env({ exprand(3, 2000.0) } ! 18, 0.2, \exp).kr,
                200,
                Env({ rrand(0.1, 0.2) } ! 18 ++ 0, 0.2).kr(2))
        }.play;
)
::

method::blend
Blend two envelopes. Returns a new Env. See link::#blend:: example below.

argument::argAnotherEnv
an Env.

argument::argBlendFrac
a number from zero to one.

method::delay
Returns a new Env based on the receiver in which the start value will be held for strong::delay:: number of seconds.

argument::delay
The amount of time to delay the start of the envelope.

discussion::
code::
a = Env.perc(0.05, 1, 1, -4);
b = a.delay(2);
a.test.plot;
b.test.plot;

a = Env([0.5, 1, 0], [1, 1]).plot;
a.delay(1).plot;
::

method::duration
Set the total duration of times, by stretching them.
discussion::
code::
e = Env([0, 1, 0], [1, 2]);
e.duration;
e.duration = 2;
e.duration;
::

method::circle
circle from end to beginning over the time specified, with the curve specified. See also the class method link::#*circle::

discussion::
code::
(
{ SinOsc.ar(
        EnvGen.kr(
                Env([6000, 700, 100], [1, 1], ['exp', 'lin']).circle.postcs)
        ) * 0.1
        + Impulse.ar(1) }.play;
)

(
{ SinOsc.ar(
        EnvGen.kr(
                Env([6000, 700, 100], [1, 1], ['exp', 'lin']).circle(1).postcs,
                MouseX.kr > 0.5)
        ) * 0.1
        + Impulse.ar(1) }.play;
)
::

method::test
Test the envelope on the default link::Classes/Server:: with a link::Classes/SinOsc::.

argument::releaseTime
If this is a sustaining envelope, it will be released after this much time in seconds. The default is 3 seconds.

method::plot
Plot this envelope's shape in a window.

argument::size
The size of the plot. The default is 400.

argument::bounds
the size of the plot window.

argument::minval
the minimum value in the plot. Defaults to the lowest value in the data.

argument::maxval
the maximum value in the plot. Defaults to the highest value in the data.

argument::parent
a window to place the plot in. If nil, one will be created for you.

method::asSignal
Returns a link::Classes/Signal:: of size strong::length:: created by sampling this Env at strong::length:: number of intervals. If the envelope has multiple channels (see link::#multichannel expansion::), this method returns an array of signals.

method::asArray
Converts the Env to an link::Classes/Array:: in a specially ordered format. This allows for Env parameters to be settable arguments in a SynthDef. See example below under link::#newClear::.

method::asMultichannelArray
Converts the Env to an link::Classes/Array:: in a specially ordered format, like link::#asArray::, however it always returns an array of these data sets, corresponding to the number of channels of the envelope.

method::isSustained
Returns true if this is a sustaining envelope, false otherwise.

method::range, exprange
Returns a copy of the Env whose levels have been mapped onto the given linear or exponential range.
discussion::
code::
a = Env.adsr;
a.levels;
a.range(42, 45).levels;
a.exprange(42, 45).levels;

(
// Mapping an Env to an exponential frequency range:
{
        SinOsc.ar(EnvGen.ar(Env.perc(0.01, 0.7).exprange(40, 10000), doneAction: 2)) * 0.2;
}.play
)
::

subsection::Client-side Access and Stream Support
Sustain and loop settings have no effect in the methods below.

method::at
Returns the value of the Env at strong::time::. If the envelope has multiple channels, this method returns an array of levels.

argument::time
A number or an array of numbers to specify a cut in the envelope. If time is an array, it returns the corresponding levels of each time value, and if the envelope has multiple channels, it returns an array of values. A combination of both returns a two-dimensional array.

discussion::
code::
e = Env.triangle(1, 1);
e.at(0.5);
e.at([0.5, 0.7]);

e = Env([1, [1, 2, 3], 1], [1, 1], \exp);
e.at(0.5);
e.at(1.8);
e.at(2);
e.at([0.5, 1.2]);

e = Env([1, 100, 1], [1, [1, 2, 3]], \exp);
e.at(0.5);
e.at(2);
e.at([1, 2, 4]);


::

method::embedInStream
Embeds this Env within an enclosing link::Classes/Stream::. Timing is derived from code::thisThread.beats::.

method::asStream
Creates a Routine and embeds the Env in it. This allows the Env to function as a link::Classes/Stream::.
discussion::
code::
(
{
e = Env.sine.asStream;
5.do({
        e.next.postln;
        0.25.wait;
})}.fork
)
::

Examples::

code::
s.boot;         //.test below will run a synthesis example
                // to demonstrate the envelope, so the Server must be on

// different shaped segments: .plot graphs the Env
Env.new([0,1, 0.3, 0.8, 0], [2, 3, 1, 4],'linear').test.plot;
Env.new([0.001, 1, 0.3, 0.8, 0.001], [2, 3, 1, 4],'exponential').test.plot;
Env.new([0, 1, 0.3, 0.8, 0], [2, 3, 1, 4],\sine).test.plot;
Env.new([0.001, 1, 0.3, 0.8, 0.001],[2,3,1,4],\welch).test.plot;
Env.new([0, 1, 0.3, 0.8, 0], [2, 3, 1, 4],'step').test.plot;
Env.new([0, 1, 0.3, 0.8, 0], [2, 3, 1, 4], -2).test.plot;
Env.new([0, 1, 0.3, 0.8, 0], [2, 3, 1, 4], 2).test.plot;
Env.new([0, 1, 0.3, 0.8, 0], [2, 3, 1, 4], [0, 3, -3, -1]).test.plot;
::

If a release node is given, and the gate input of the EnvGen is set to zero, it outputs the nodes after the release node:

code::
// release node is node 1; takes 0.5 seconds to go from 0 to 1,
// sustains at level of 1, then released after three seconds
// (test causes the release after three seconds, given the argument 3),
// taking 2 seconds to finish
Env.new([0,1,0],[0.5,2],'linear',1).test(3).plot

// more complex examples
// release node is node 2; releases after 5 sec
Env.new([0.001,1,0.3,0.8,0.001],[2,3,1,4] * 0.2, 2, 2).test(5).plot;
Env.new([0.001,1,0.3,0.8,0.5,0.8,0],[2,3,1,2,2,1] * 0.2, 2, 2).test(5).plot;

// early release: goes straight onto the release node after 0.1 seconds
Env.new([0.001,1,0.3,0.8,0.5,0.8,0],[2,3,1,2,2,1] * 0.2, 2, 2).test(0.1).plot;
::

If a loop node is given, the EnvGen outputs the nodes between the loop node and the release node (not including the release node itself) until it is released:

code::
// release node is node 2, loop node is node 0: so loops around nodes 0 (lvl 1, dur 0.5)
// and 1 (lvl 0.1, dur 0.5)             //until released after 3.5 seconds
Env.new([0,1,0.1,0],[0.5,0.5,2], 'lin', 2, 0).test(3.5).plot;

// this just sustains at node 0, because there is no other node to loop around!
Env.new([0,1,0],[0.5,2], 'lin', 1, 0).test(3.5).plot;

// more complex example: release node is node 3, loop node is node 1
Env.new([0.001,1,0.3,0.8,0.5,0.8,0],[2,1,1,2,3,1] * 0.1, 'lin', 3, 1).test(3).plot;
::

note::
The starting level for an envelope segment is always the level you are at right now. For example when the gate is released and you jump to the release segment, the level does not jump to the level at the beginning of the release segment, it changes from whatever the current level is to the goal level of the release segment over the specified duration of the release segment.

There is an extra level at the beginning of the envelope to set the initial level. After that each node is a goal level and a duration, so node zero has duration equal to times[0] and goal level equal to levels[1].

The loop jumps back to the loop node. The endpoint of that segment is the goal level for that segment and the duration of that segment will be the time over which the level changed from the current level to the goal level.
::

subsection::newClear
code::
(
SynthDef(\help_Env_newClear, { |out = 0|
        var env, envctl;
        // make an empty 4 segment envelope
        env = Env.newClear(4);
        // create a control argument array
        envctl = \env.kr(env.asArray);
        Out.ar(out, SinOsc.ar(EnvGen.kr(envctl, \gate.tr), 0, 0.3)); // the gate control is a trigger
}).add;
)

Synth(\help_Env_newClear, [\gate, 1, \env, Env([700,900,900,800], [1,1,1], \exp)]); // 3 segments

// reset then play again:
Synth(\help_Env_newClear, [\gate, 1, \env, Env({ rrand(60, 70).midicps } ! 4, [1,1,1], \exp)]);

// the same written as an event:
(instrument: \help_Env_newClear, gate: 1, env: Env({ rrand(60, 70).midicps } ! 4, [1,1,1], \exp)).play;

::

note:: The above technique currently doesn't work with multichannel expanded envelopes (See: link::#multichannel expansion::)::



subsection::blend
code::
a = Env([0, 0.2, 1, 0.2, 0.2, 0], [0.5, 0.01, 0.01, 0.3, 0.2]);
a.test.plot;

b = Env([0, 0.4, 1, 0.2, 0.5, 0], [0.05, 0.4, [0.01, 0.1], 0.1, 0.4]);
b.test.plot;

(
Task({
        f = (0, 0.2 .. 1);
        f.do { |u|
                blend(a, b, u).test.plot;
                2.wait;
                Window.allWindows.pop.close; // close last opened window
        }
}).play(AppClock);
)

// blend in a SynthDef
(
SynthDef(\help_EnvBlend, { | factor = 0 |
        Out.ar(0, EnvGen.kr(blend(Env.perc, Env.sine, factor), 1.0, doneAction: 2)
                * SinOsc.ar(440,0,0.1)
        )
}).add
);

(
{
        var factors = (0, 0.1..1);
        factors.do {|f| Synth(\help_EnvBlend, [\factor, f.postln]); 1.wait };
}.fork
);
::