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Description:

klang 0.2.1

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

Getting Started

Prerequisites
We use Python bindings for PortAudio and RtMidi. On Mac they can be installed via
Homebrew.

Installing
Klang can be installed via PyPi / pip or directly via setup.py. Note that there
are some audio C extensions. Python fallbacks exists.
python3 setup.py build_ext --inplace
For developing you can link your working copy with
python3 setup.py develop

Running the tests
Tests can be run via with
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.
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.
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.

# Pipe operator
a | b | c

# Is equivalanet to:
# >>> a.output.connect(b.input)
# ... b.output.connect(c.input)
# 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: 440 Hz sine wave generator
aeolian_arp.py: More fun with random ever changing arpeggios.
arpeggiator_demo.py: Two synthesizer patch with an arpeggiator and some sound effects
audio_file_demo.py: Looped audio file playback (gong.wav sample) with audio effects
haunting_envelopes.py: Multiple oscillators controlled by looping envelopes
micro_rhythm_demo.py: Kick and Hi-Hat pattern where the latter is phrased with a micro rhythm
reverberation_demo.py: Ambient loop showcasing the reverb effect.
sequencer_demo.py: Techno patch with sequencer
synthesizer_demo.py: This has to be started as root. Computer keyboard playable monophonic synthesizer
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)

Acknowledgments
Thanks for the support and inputs!

Nico Neureiter
Andreas Steiner
Lawrence Markwalder