PyCodeDJ Manual

1. What is PyCodeDJ?

In one sentence

PyCodeDJ is an instrument where writing Python code changes the music in real time.

Add more for loops and the modulation speeds up. Write three functions and you get three-voice polyphony. Fill the file with comments and the reverb deepens. Write pattern("x . x .") and that rhythm plays. Write pattern("0 . 3 . 5 .") and those pitches ring out.

from pycodedj import loop, pattern

# Code structure controls the sound
@loop("bass", interval=2.0)
def bass_line(volume=0.4):
    for i in range(8):
        if i % 2 == 0:
            pass

# pattern() specifies rhythm and pitch explicitly
@loop("kick", synth="floor_kick", dur=0.25)
def kick_drum():
    pattern("x . x .")

@loop("melody", synth="acid_lead", root="A3", scale="minor", dur=0.25)
def melody_line():
    pattern("0 . 3 . 5 . 7 .")

Save this file and the sound changes instantly. No extra configuration needed.

What can you do with it?

• Live-coding performance — perform music in front of an audience by writing code
• Sonic feedback while coding — feel the structure of what you write, in real time
• Programming education — immediate auditory feedback for every code change

Where does the sound come from?

PyCodeDJ itself does not produce sound. SuperCollider (a free software audio synthesizer) does. PyCodeDJ is the bridge — it analyzes your Python code and sends parameters to SuperCollider over OSC.

You write Python code and save
         |
         v
   PyCodeDJ analyzes the code
   (nesting depth, function count,
     comment ratio, pattern() content…)
         |
         | OSC messages
         v
   SuperCollider plays the sound
         |
         v
      Speakers

You only interact with SuperCollider once at the start. After that, it stays in the background.

2. Installation

Requirements

• Python 3.10 or later — check with python --version or python3 --version
• SuperCollider 3.12 or later — instructions in the next section

Install PyCodeDJ

pip install 'pycodedj[watch]'

The [watch] extra enables file watching so you can use the watch command. Install it from the start — it makes live-coding much smoother.

Verify the installation:

pycodedj --help

You should see:

usage: pycodedj [-h] [--version] {eval,watch,panic,stop,mute,unmute,solo,unsolo,status} ...

Development install

git clone https://github.com/kanekoyuichi/pycodedj
cd pycodedj
pip install -e ".[dev]"

3. Setting up SuperCollider

SuperCollider handles all audio output. You only need to configure it once.

Install SuperCollider

Download from the official site (supercollider.github.io):

• macOS: Download the .dmg and install
• Linux: Use your package manager or the official site (sudo apt install supercollider on Ubuntu)
• Windows: Download the .exe installer

After installation, launch SuperCollider IDE. If the window opens, you're good.

The SuperCollider IDE

There are two main areas:

• Code area (top): Where you type and run SuperCollider code like s.boot;
• Post window (right or bottom): Where output, logs, and errors appear

When this manual says "run in SuperCollider," it means the code area in SuperCollider IDE — not your terminal.

Step 1: Boot the server

In the SuperCollider code area, type this and press Ctrl+Enter (Mac: Cmd+Enter):

s.boot;

The indicator at the bottom turns green when the server is running.

Tip: You can also use the menu: Server > Boot Server.

Step 2: Load the synths

Open sc/synths.scd from the PyCodeDJ project folder using File > Open.

Press Ctrl+A (Mac: Cmd+A) to select all, then Ctrl+Enter (Mac: Cmd+Enter) to run.

When the Post window shows this, you're ready:

PyCodeDJ synths loaded. Ready. OSC port: 57120

If this doesn't appear, see Troubleshooting.

Note: After restarting SuperCollider, run sc/synths.scd again.

Step 3: Verify the connection

Back in your terminal, run:

pycodedj eval examples/demo.py::bass

If the terminal shows [pycodedj] bass ... and SuperCollider plays a sound, the connection works.

4. Making your first sound

Loop file basics

A PyCodeDJ file looks like this:

from pycodedj import loop

@loop("name", interval=seconds)
def function_name(volume=level):
    # The structure of this code maps to sound
    ...

The @loop("name", interval=seconds) decorator makes a function a "loop":

• "name" — the name sent to SuperCollider (letters, numbers, underscores)
• interval=seconds — update interval in seconds (default: 1.0)
• volume=level — volume from 0.0 to 1.0 (default: 0.3)

Try the demo file

Open examples/demo.py:

from pycodedj import loop

@loop("bass", interval=2.0)
def bass(volume=0.4):
    for i in range(8):
        if i % 2 == 0:
            pass

@loop("melody", interval=0.5)
def melody(volume=0.3):
    x = 1
    y = 2
    return x + y

@loop("pad", interval=4.0)
def pad(volume=0.15):
    # leave space here
    # a little more
    # silence is music
    pass

Evaluate the bass loop:

pycodedj eval examples/demo.py::bass

On success:

[pycodedj] bass  cutoff=418Hz  lfo=1.08Hz  reverb=0.00  voices=1  amp=0.40

Now evaluate melody and pad:

pycodedj eval examples/demo.py::melody
pycodedj eval examples/demo.py::pad

All three loops are playing simultaneously, independently.

Change the code, change the sound

Open examples/demo.py in an editor and deepen the nesting in the bass block:

Before:

@loop("bass", interval=2.0)
def bass(volume=0.4):
    for i in range(8):
        if i % 2 == 0:
            pass

After:

@loop("bass", interval=2.0)
def bass(volume=0.4):
    for i in range(8):
        for j in range(4):      # added
            if i % 2 == 0:
                if j > 2:       # added
                    pass

Save, then re-evaluate:

pycodedj eval examples/demo.py::bass

[pycodedj] bass  cutoff=1200Hz  lfo=2.16Hz  reverb=0.00  voices=1  amp=0.40

The filter opened up and the modulation got faster. Deeper nesting = brighter sound.

5. Watch mode — save to reload

Running pycodedj eval manually each time gets tedious. The watch command evaluates all loops at startup and then re-evaluates automatically on every save.

Start watching

pycodedj watch examples/demo.py

[pycodedj] watching demo.py — save to reload (Ctrl+C to stop)
[pycodedj] reloaded demo.py (3 loop(s))

All loops play immediately. From here, just write code and save. Every save shows:

[pycodedj] reloaded demo.py (3 loop(s))

Write code → Save → Sound changes. That's the live-coding workflow.

Stop watching

Press Ctrl+C. The SuperCollider sound keeps playing. Use pycodedj panic to stop all sound.

Syntax errors

If you save with a syntax error, only that loop stays unchanged. The rest keep playing. The error appears in the terminal:

[pycodedj] syntax error (bass): invalid syntax (demo.py, line 7)

Fix the syntax and save to recover automatically.

6. How code structure maps to sound

PyCodeDJ reads the shape of your code — not what it computes — and maps it to five musical parameters.

Mapping table

Note: Arithmetic expressions like x = 1 + 2 * (3 + 4) are not counted. Only block-level structure (if, for, while, def) matters.

Examples

Filter brightness (nesting depth)

# Nesting depth 0 → filter minimum (dark, muffled sound)
@loop("dark", interval=1.0)
def f(volume=0.3):
    pass

# Nesting depth 4 → filter maximum (bright, open sound)
@loop("bright", interval=1.0)
def f(volume=0.3):
    for i in range(4):
        for j in range(4):
            if i == j:
                pass

Modulation speed (control-flow count)

# 0 control-flow statements → minimal modulation (steady)
@loop("still", interval=1.0)
def f(volume=0.3):
    pass

# 3 control-flow statements → fast modulation
@loop("busy", interval=1.0)
def f(volume=0.3):
    for i in range(4):     # 1
        if i > 2:          # 2
            while False:   # 3
                pass

Polyphony (function count)

# 1 function → mono (solo)
@loop("solo", interval=1.0)
def f(volume=0.3):
    pass

# 4 functions → 4-voice polyphony (maximum)
@loop("choir", interval=1.0)
def f(volume=0.3):
    def voice_a(): pass
    def voice_b(): pass
    def voice_c(): pass
    def voice_d(): pass

Space / reverb (comment ratio)

# No comments → dry sound
@loop("dry", interval=1.0)
def f(volume=0.3):
    x = 1
    return x

# Many comments → deep reverb
@loop("spacious", interval=1.0)
def f(volume=0.3):
    # space
    # more space
    # silence is music
    pass

EQ

@loop("bass_reese", interval=0.5)
def bass(volume=0.45, eq="edm"):
    ...

@loop("hat_engine", interval=0.25)
def hats(volume=0.08, eq="edm", low=0.5, high=1.25):
    ...

7. pattern() — specify rhythm and pitch

Beyond code-structure mapping, you can specify rhythm and pitch explicitly using pattern().

The basics

from pycodedj import loop, pattern

@loop("kick", synth="floor_kick", dur=0.25)
def kick_drum():
    pattern("x . x .")

The string passed to pattern() describes a sequence of steps:

Tokens are separated by spaces. "x . x ." is a 4-step pattern.

@loop arguments for pattern mode

Choose the sound with synth=. @loop("bass", synth="floor_kick") keeps the loop name as bass, but plays the floor_kick synth.

volume=, eq=, and interval= still work alongside pattern arguments. In @loop("kick", synth="floor_kick"), "kick" is the loop name and "floor_kick" is the synth name. Use the loop name for commands such as pycodedj eval demo.py::kick and pycodedj mute kick.

Trigger patterns — x and . only

When you only want rhythm without specific pitches, use x and .:

from pycodedj import loop, pattern

@loop("kick", synth="floor_kick", dur=0.25)
def kick():
    pattern("x . x .")           # 4 steps

@loop("hat", synth="hat_engine", dur=0.25)
def hat():
    pattern("x x x x x x x x")  # 8 steps (16th-note grid)

@loop("snare", synth="clap_snare", dur=0.25)
def snare():
    pattern(". . x . . . x .")   # backbeat (beats 2 and 4)

Pitch patterns — scale degrees

Use non-negative integers to specify pitch as a scale degree:

@loop("melody", synth="acid_lead", root="A3", scale="minor", dur=0.25)
def melody():
    pattern("0 . 3 . 5 . 7 .")

With scale="minor" and root="A3", the degrees map like this:

Degrees above 6 automatically wrap up by an octave. 7 = one octave above 0, 14 = two octaves above 0.

Available scales

Any scale from SuperCollider's Scale library works. Common ones:

Mixing x and degrees

You can mix trigger tokens and degrees in the same pattern. x plays at the root note.

@loop("bass", synth="acid_lead", root="C3", scale="minor", dur=0.25)
def bass():
    pattern("0 . x . 3 . x .")
    # 0→C3, rest, x→C3, rest, 3→Eb3, rest, x→C3, rest

Chords — multiple notes at once

Wrap multiple degrees in square brackets to play them simultaneously in one step:

@loop("chord", synth="note", root="C3", scale="minor", dur=0.5)
def chord():
    pattern("[0 2 4] . [0 3] .")
    # [0 2 4]→C3+Eb3+G3 (minor triad), rest, [0 3]→C3+Eb3, rest

Only non-negative integers are allowed inside brackets. ., x, and ~ are not valid inside a chord.

Ties — sustaining a note

Use ~ to extend the previous note or chord by one additional step:

@loop("bass", synth="note", root="A1", scale="minor", dur=0.25)
def bass():
    pattern("0 . [0 3] ~ 5 . 3 .")
    # 0→A1, rest, [0 3] chord held for 2 steps, 5→F2, rest, 3→D2, rest

~ can only follow a degree or chord. Placing it at the start, or after . or x, raises a ValueError.

Root note notation

Full example: kick, bass, and chord

from pycodedj import loop, pattern

@loop("kick", synth="floor_kick", dur=0.25)
def kick():
    pattern("x . . . x . . .")

@loop("bass", synth="bass_acid", root="A1", scale="minor", dur=0.25)
def bass():
    pattern("0 . [0 3] ~ 5 . 3 .")
    # 0→A1, rest, [0 3] chord held for 2 steps, 5→F2, rest, 3→D2, rest

@loop("melody", synth="acid_lead", root="A3", scale="minor", dur=0.5)
def melody():
    pattern("0 3 5 7")

@loop("pad", interval=4.0)
def pad(volume=0.06):
    # ambient background
    # let the code breathe
    pass

pattern() vs code-structure mapping

Both styles can coexist in the same file.

8. Running multiple loops

The key feature of PyCodeDJ is that multiple loops run independently. Updating one loop doesn't interrupt the others.

Basic setup

from pycodedj import loop, pattern

@loop("kick", synth="floor_kick", dur=0.25)
def kick():
    pattern("x . x .")

@loop("bass", interval=2.0)
def bass_line(volume=0.4):
    for i in range(8):
        if i % 2 == 0:
            pass

@loop("pad", interval=4.0)
def atmosphere(volume=0.08):
    # ambient space
    # breathe
    pass

Start watching and each save updates only the changed loops:

pycodedj watch myfile.py

Try the sub-heavy club set

examples/club_set.py is a low-end club-floor example. It layers a four-on-the-floor kick, clap on beats 2 and 4, offbeat hats, 16th-note hats, rumble, sub bass, acid bass, sparse stabs, fills, and room noise.

pycodedj watch examples/club_set.py

These are the main loop names. Use mute / unmute to bring layers in and out and hear how the groove is built.

Live controls

Stop, mute, and unmute

pycodedj stop bass        # stop bass
pycodedj mute bass        # silence without stopping
pycodedj unmute bass      # restore volume

Emergency stop

pycodedj panic            # stop everything immediately

Check loop status

pycodedj status

Loop         State    Amp    Cutoff
kick         playing  0.30   —
bass         playing  0.40   1340Hz
pad          muted    0.08   200Hz

Removing a loop

Delete the @loop block (decorator + function) and save. In watch mode, the loop stops automatically.

9. Sound Reference

PyCodeDJ has two related names:

• Loop name: the first argument to @loop("kick", ...). Use it with pycodedj eval demo.py::kick, mute, solo, and status commands.
• Synth name: the SuperCollider synth name. Pattern loops set it with synth="floor_kick".

To choose a sound, pick a synth name from the tables below and put it in synth=. For example, @loop("bass", synth="floor_kick") creates a loop called bass that plays the floor_kick synth.

With pattern(), you can keep these names separate: @loop("kick", synth="floor_kick") means the loop is called kick, and it plays the floor_kick synth.

For non-pattern structure-mapping loops, PyCodeDJ keeps the older shorthand: if the loop name matches a synth name, that synth is used. For example, @loop("bass_acid", interval=0.5) plays the bass_acid synth.

To audition all 30 synths one at a time, use examples/sound_showcase.py:

pycodedj eval examples/sound_showcase.py::floor_kick
pycodedj eval examples/sound_showcase.py::bass_acid
pycodedj eval examples/sound_showcase.py::acid_lead

In examples/sound_showcase.py, loop names intentionally match synth names so each sound is easy to audition. In normal pattern loops, put one of the synth names below in synth=:

@loop("kick", synth="floor_kick", dur=0.25)
def kick():
    pattern("x . x .")

Kick

Bass

Percussion

Chords / Stabs

Lead / Melody

Atmosphere

FX

10. Performance ideas

Idea A: Grow from silence

Start with empty code and add elements one save at a time. Each save is an audible step.

# Stage 1: minimum (dark filter, mono)
@loop("main", interval=1.0)
def f(volume=0.3):
    pass

# Stage 2: add movement
@loop("main", interval=1.0)
def f(volume=0.3):
    for i in range(4):
        pass

# Stage 3: open the filter with deeper nesting
@loop("main", interval=1.0)
def f(volume=0.3):
    for i in range(4):
        for j in range(2):
            if i > j:
                pass

# Stage 4: climax — maximum polyphony
@loop("main", interval=1.0)
def f(volume=0.5):
    def voice_a():
        for i in range(4):
            for j in range(2):
                if i > j:
                    pass
    def voice_b():
        for k in range(8):
            pass

Idea B: Live sequence with pattern()

Change the pattern string on each save.

from pycodedj import loop, pattern

@loop("kick", synth="floor_kick", dur=0.25)
def kick():
    pattern("x . x .")     # ← change this and save to change the rhythm

@loop("bass", synth="bass_acid", root="A1", scale="minor", dur=0.25)
def bass():
    pattern("0 . 0 . 3 .") # ← change degrees to change the harmony

Idea C: Contrast quiet and loud

Pair a busy loop with a spacious one.

@loop("bass", interval=2.0)
def the_bass(volume=0.5):
    def layer_a():
        for i in range(8):
            for j in range(4):
                if i == j:
                    pass
    def layer_b():
        for k in range(8):
            pass

@loop("pad", interval=4.0)
def space(volume=0.08):
    # silence
    # more silence
    # just space
    pass

Idea D: Perform with comments only

Leave one function and change only the comment count. More comments = more reverb.

@loop("ambient", interval=4.0)
def f(volume=0.15):
    # add or remove lines here to change the space
    pass

Idea E: Write a story with function names

Sound comes from code structure, not function names. Name things whatever you like.

@loop("scene", interval=2.0)
def the_city_wakes_up(volume=0.3):
    for hour in range(6):
        if hour > 4:
            pass

@loop("rush", interval=1.0)
def rush_hour(volume=0.2):
    for commuter in range(8):
        for train in range(3):
            if commuter % 2 == 0:
                pass

11. Troubleshooting

No sound

First, check that SuperCollider works on its own. In the SuperCollider code area:

{ SinOsc.ar(440, 0, 0.1) ! 2 }.play;

Ctrl+Enter to run, Ctrl+. (Mac: Cmd+.) to stop.

If this produces no sound, the issue is with SuperCollider, not PyCodeDJ. Check your system volume, output device, and audio server.

If it does produce sound, work through these checks:

1. Is the server booted?

s.boot;

2. Is sc/synths.scd loaded?

Select all (Ctrl+A) and run (Ctrl+Enter). The Post window should show:

PyCodeDJ synths loaded. Ready. OSC port: 57120

3. Is the port number correct?

Run this in SuperCollider:

NetAddr.langPort.postln;

If it shows something other than 57120, specify it:

pycodedj eval examples/demo.py::bass --sc-port PORT_NUMBER

4. Trace OSC messages

OSCFunc.trace(true);

Run pycodedj eval and check whether messages appear in the Post window. Disable tracing when done:

OSCFunc.trace(false);

[pycodedj] OSC error

SuperCollider isn't running or the port number is wrong.

1. 1. Check that SuperCollider IDE is open and the server is booted
2. 2. Run sc/synths.scd and confirm Ready. in the Post window
3. 3. If the port differs from 57120, use --sc-port

loop 'xxx' not found

The loop name after :: doesn't match the first argument of @loop(...).

# If the file contains @loop("bass", ...)
pycodedj eval demo.py::bass   # correct
pycodedj eval demo.py::Bass   # wrong (case sensitive)

file not found

Check your current directory and use an absolute path if needed.

pwd    # show current directory
ls     # list files

pycodedj eval /home/user/projects/myfile.py::bass

pycodedj watch asks you to install watchdog

pip install 'pycodedj[watch]'

Output device changed and now there's no sound

SuperCollider uses the output device that was active when the server booted. After changing the device:

ServerOptions.devices;  // list available devices

s.quit;
s.options.outDevice = "Your Device Name";
s.options.numInputBusChannels = 0;
s.boot;

Then run sc/synths.scd again.

12. Full command and option reference

pycodedj eval

Evaluate one loop and send parameters to SuperCollider.

pycodedj eval FILE::LOOP [--sc-host HOST] [--sc-port PORT]

On success, stdout shows:

[pycodedj] bass  cutoff=418Hz  lfo=1.08Hz  reverb=0.00  voices=1  amp=0.40

On failure, stderr shows an error and exit code is 1.

pycodedj eval examples/demo.py::bass
pycodedj eval demo.py::melody --sc-host 192.168.1.10
pycodedj eval demo.py::pad --sc-port 57200

pycodedj watch

Watch a file and re-evaluate all loops at startup and on every save. Stop with Ctrl+C.

pycodedj watch FILE [--sc-host HOST] [--sc-port PORT] [--debounce SECS]

pycodedj watch examples/demo.py
pycodedj watch examples/club_set.py --debounce 0.5

pycodedj panic

Send an immediate stop signal to all active loops.

pycodedj panic [--sc-host HOST] [--sc-port PORT]

pycodedj panic

pycodedj stop

Stop one loop by name. Unlike mute, this stops both the legacy synth loop and the pattern() Pdef for that loop.

pycodedj stop NAME [--sc-host HOST] [--sc-port PORT]

pycodedj stop kick_hard

pycodedj mute

Silence a loop without stopping it.

pycodedj mute NAME [--sc-host HOST] [--sc-port PORT]

pycodedj mute bass

pycodedj unmute

Restore a muted loop's volume.

pycodedj unmute NAME [--sc-host HOST] [--sc-port PORT]

pycodedj unmute bass

pycodedj status

Show the state of all active loops.

pycodedj status [--sc-host HOST] [--sc-port PORT]

Loop         State    Amp    Cutoff
bass         playing  0.40   1340Hz
pad          muted    0.15   200Hz

Note: status runs in a separate process from watch and can only see loops that watch is currently managing.

Loop syntax summary

from pycodedj import loop, pattern

# Code-structure mode
@loop("name", interval=seconds)
def function_name(volume=level, eq="preset"):
    # code structure maps to sound
    ...

# pattern() mode
@loop("name", synth="synth_name", root="note", scale="scale_name", dur=seconds)
def function_name(volume=level):
    pattern("x . x . 0 . 3 .")

13. Under the hood

Mapping numbers

OSC address reference

Use these addresses to connect external tools like Hydra.

Using the Python API directly

from pycodedj.block_parser import parse_blocks
from pycodedj.engine import Engine
from pycodedj.osc_bridge import OscBridge, OscEndpoint

bridge = OscBridge(audio=OscEndpoint("127.0.0.1", 57120))
engine = Engine(bridge=bridge)

source = open("demo.py").read()
blocks = {b.name: b for b in parse_blocks(source).blocks}

params = engine.eval_block(blocks["bass"])
if params is not None:
    print(f"cutoff={params.cutoff:.0f}Hz  amp={params.amp:.2f}")

eval_block returns MusicParams on success, or None on syntax error or OSC failure.

Module overview

pycodedj/
├── _loop.py          # @loop decorator (no-op at runtime)
├── block_parser.py   # AST parser: extracts @loop blocks from source
├── analyzer.py       # Feature extraction: depth, counts, ratios
├── mapper.py         # Maps features to MusicParams
├── pattern.py        # Parses pattern() strings to step lists
├── engine.py         # Evaluation pipeline
├── osc_bridge.py     # OSC communication with SuperCollider
├── watcher.py        # File watcher (watchdog-based)
└── __main__.py       # CLI entry point