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Defining a Patch

A Patch is made up of a connected network of Nodes, together with a set of properties that determine how the Patch can be controlled.

There are two general ways to define the structure of a Patch:

  • Create a new class that subclasses Patch. In general, this is the recommended approach for defining new Patches.
  • Create a JSON file that can be loaded as a PatchSpec, which describes the structure of a patch

Creating a Patch subclass

The quickest and most intuitive way to define a Patch is by subclassing the Patch class itself. Let's look at an example.

class Bleep (Patch):
    def __init__(self, frequency=880, duration=0.1):
        frequency = self.add_input("frequency", frequency)
        duration = self.add_input("duration", duration)
        sine = SineOscillator(frequency)
        env = ASREnvelope(0.001, duration, 0.001)
        output = sine * env

In the above example:

  • At the very start of the __init__ function, super().__init__() must be called to initialise the Patch and its storage. This is vital! Without it, your program will crash.
  • Two audio-rate input parameters are defined. The add_input() method is used to define them as inputs of the Patch, which can then be subsequently modulated. Note that the add_input() method returns a reference to the frequency node, which then acts as a pointer to the input node.
  • self.set_output() is used to define the Patch's output. A Patch can only have one single output.
  • Finally, self.set_auto_free() is used to automatically stop and free the Patch after playback of the envelope is completed. More about auto-free...

You can now instantiate a Bleep object in just the same way as you would instantiate and play a Node:

b = Bleep(frequency=440, duration=0.2)

If you query graph.status after playback has finished, you should see that the Patch is automatically freed and the number of nodes returns to 0.

Creating a PatchSpec from JSON

The structure of a Patch is described by a PatchSpec, which can in turn be imported/exported in the JSON text-based data interchange format.

For information on loading or saving PatchSpecs as JSON, see Exporting and importing patches.

→ Next: Playing and stopping a Patch

Last update: 2023-01-03
Created: 2022-04-02