klang 0.2.1
Block based synthesis and music library
Requires Python: >=3.0
Keywords: synthesis music library

Klang
=====

Block based synthesis and music library for Python. *Klang* is German for sound.

Getting Started
---------------

Prerequisites
^^^^^^^^^^^^^

We use Python bindings for `PortAudio <http://www.portaudio.com>`_ and `RtMidi
<https://www.music.mcgill.ca/~gary/rtmidi/>`_. On Mac they can be installed via
`Homebrew <https://brew.sh>`_.

Installing
^^^^^^^^^^

Klang can be installed via PyPi / pip or directly via setup.py. Note that there
are some audio C extensions. Python fallbacks exists.

.. code-block:: bash

    python3 setup.py build_ext --inplace

For developing you can link your working copy with

.. code-block:: bash

    python3 setup.py develop

Running the tests
-----------------

Tests can be run via with

.. code-block:: bash

    python3 setup.py test

Safety First
------------

As always when programming with sound: Unplug your headphones or be very sure of
what you are doing! Also with low headphone volume bugs in the code can result
in very unpleasant loud noises which could probably impair your hearing. Be
careful!

Klang Primer
------------

Klang provides various audio related blocks. Every block can have multiple in-
and outputs and by connecting them with each other we can define our network.
Once we are finished with patching we can run our network with by calling
`run_klang(*blocks)`. This function only needs some blocks which belong to the
network. It will then automatically discovers the other blocks of the network
and deduce an appropriate block execution order.

In the following script we create a 440 Hz sine oscillator which output gets
send to the sound card.

.. code-block:: python

    from klang.audio import Oscillator, Dac
    from klang.klang import run_klang

    # Init blocks
    osc = Oscillator(frequency=440.)
    dac = Dac(nChannels=1)

    # Define network
    osc.output.connect(dac.input)

    # Run it
    run_klang(dac)

Audio can be written to disk as a WAV file with the `filepath` argument.

.. code-block:: python

    run_klang(*blocks, filepath='some/filepath.wav')

Connections
^^^^^^^^^^^

There are two different types of connections in Klang:

Value
  These connection can hold any kind of Python object which will be propagated
  through the network and updated during each cycle. Most commonly these are
  numpy arrays holding audio or modulation signals (``Input`` and ``Output``
  classes).

Message
  Discrete messages. Each message input has its own internal message queue. Most
  commonly ``Note`` messages (``MessageInput`` and ``MessageOutput`` classes).

There are also corresponding *Relay* connections (``Relay`` and ``MessageRelay``
classes). These are used to build composite blocks (blocks which contain there
own network of child blocks). Relays can be used to interface between the inside
and outside of an composite block.

Defining The Network
^^^^^^^^^^^^^^^^^^^^

The ``connect`` method can be used to connect inputs and outputs with each other.
Note that it is always possible to connect one output to multiple inputs but not
the other way round. As a shorthand there are two overloaded operators:

- Pipe operator ``|``: Connect multiple blocks in series.
- Mix operator ``+``: Mix multiple value outputs together.

.. code-block:: python

    # Pipe operator
    a | b | c

    # Is equivalanet to:
    # >>> a.output.connect(b.input)
    # ... b.output.connect(c.input)

.. code-block:: python

    # Mix operator
    mixer = a + b + c

    # Is equivalanet to:
    # >>> mixer = Mixer(nInputs=0)
    # ... mixer.add_new_channel()
    # ... a.output.connect(mixer.inputs[-1])
    # ... mixer.add_new_channel()
    # ... b.output.connect(mixer.inputs[-1])
    # ... mixer.add_new_channel()
    # ... c.output.connect(mixer.inputs[-1])

Examples
--------

See the ``examples`` directory with a couple example script which illustrate the
core functionality of Klang. Currently there are:

- `hello_world.py <https://github.com/atheler/klang/blob/master/examples/hello_world.py>`_: 440 Hz sine wave generator
- `aeolian_arp.py <https://github.com/atheler/klang/blob/master/examples/aeolian_arp.py>`_: More fun with random ever changing arpeggios.
- `arpeggiator_demo.py <https://github.com/atheler/klang/blob/master/examples/arpeggiator_demo.py>`_: Two synthesizer patch with an arpeggiator and some sound effects
- `audio_file_demo.py <https://github.com/atheler/klang/blob/master/examples/audio_file_demo.py>`_: Looped audio file playback (`gong.wav` sample) with audio effects
- `haunting_envelopes.py <https://github.com/atheler/klang/blob/master/examples/haunting_envelopes.py>`_: Multiple oscillators controlled by looping envelopes
- `micro_rhythm_demo.py <https://github.com/atheler/klang/blob/master/examples/micro_rhythm_demo.py>`_: Kick and Hi-Hat pattern where the latter is phrased with a micro rhythm
- `reverberation_demo.py <https://github.com/atheler/klang/blob/master/examples/reverberation_demo.py>`_: Ambient loop showcasing the reverb effect.
- `sequencer_demo.py <https://github.com/atheler/klang/blob/master/examples/sequencer_demo.py>`_: Techno patch with sequencer
- `synthesizer_demo.py <https://github.com/atheler/klang/blob/master/examples/synthesizer_demo.py>`_: This has to be started as root. Computer keyboard playable monophonic synthesizer
- `tempo_aware_effects.py <https://github.com/atheler/klang/blob/master/examples/tempo_aware_effects.py>`_: Modulated noise with time synced effects

Coding Style
------------

PEP8 / Google flavored. With the one exception for variable and argument names
(`camelCase`). Function and in methods are `snake_case()`.

Author
------

* **Alexander Theler** (`GitHub <https://github.com/atheler>`_)

Acknowledgments
---------------

Thanks for the support and inputs!

- `Nico Neureiter <https://github.com/NicoNeureiter>`_
- `Andreas Steiner <http://smokeandmirrors.ch>`_
- `Lawrence Markwalder <https://github.com/lmarkwalder>`_