Cloudbuster

A command-line phase-vocoder sampler. It loads a folder of audio files, precomputes pitch-shifted samples across a MIDI note range using a phase-vocoder algorithm, and plays them back in real time via MIDI input. Time-stretching is independently controllable from pitch.

Supports 4-voice polyphony, real-time MIDI CC control, and several vocal/spectral effects.

Building

• Clone with submodules: git clone --recurse-submodules or run git submodule update --recursive --init after cloning.
• On Linux, install ALSA dev kit: sudo apt-get install libasound-dev. See PortAudio docs for other platforms.
• Create a build dir, cd into it, and run cmake ..
• Run make to build.

Usage

./cloudbuster -f <folder> [options] [effects]

-f points to a folder containing audio files (.wav, .aif, .aiff, .flac, .ogg). All files in the folder are loaded and can be cycled through via MIDI.

Flags

Flag	Description
-f <path>	Folder of audio files to load (default: .)
-n <int>	FFT size / window size (default: 1024)
-h <int>	Hop size divider — hop = window / this value (default: 8)
-s <float>	Time-stretch factor (default: 2.0)
-fs <float>	Internal sample rate (default: 8000)
-min <int>	Lowest MIDI note to precompute (default: 40)
-max <int>	Highest MIDI note to precompute (default: 90)
-midi <int>	MIDI port number to read from (default: 1)
-device <int>	PortAudio output device number (default: 0)

Effects (startup flags)

Flag	Description
roboto	Enable robotization effect
whisper	Enable whisper effect
alien	Enable alien/ring-mod effect
no-precompute	Skip precomputation (samples are computed on demand)

MIDI CC Control

All parameters can be changed at runtime via MIDI Control Change messages.

CC	Name	Range / Steps
7	Volume	0–127 → 0.0–1.0
20	N (FFT size)	0–31→512, 32–63→1024, 64–95→2048, 96–127→4096
21	Hop divisor	0–31→2, 32–63→4, 64–95→8, 96–127→16
22	Stretch	0–127 → 0.25–4.0
47	Previous file	trigger (velocity > 0)
48	Next file	trigger (velocity > 0)
72	Release time	0–127 → 0–3 s
73	Attack time	0–127 → 0–2 s
75	Decay time	0–127 → 0–2 s
79	Sustain level	0–127 → 0.0–1.0
80	Roboto toggle	trigger (velocity > 0)
81	Whisper toggle	trigger (velocity > 0)
82	Alien toggle	trigger (velocity > 0)

Changes to N, hop divisor, and stretch trigger a debounced voice rebuild.

midi.py — Test Script

midi.py is a Python helper for sending MIDI messages to a running Cloudbuster instance from the terminal. It uses amidi (raw MIDI) and aconnect (ALSA sequencer) and requires a VirMIDI kernel module (modprobe snd-virmidi).

Setup (one-time per session)

# Find available ports
./midi.py --list

# Connect VirMIDI → Cloudbuster (auto-detected)
./midi.py --connect

Examples

./midi.py note 60                  # play middle C for 0.5s
./midi.py note 60 100 -d 2         # note 60, velocity 100, 2s duration
./midi.py cc 7 100                 # raw CC message
./midi.py volume 100               # set volume
./midi.py stretch 64               # set stretch (~2.1x)
./midi.py N 64                     # set N → 2048
./midi.py hop 96                   # set hop divisor → 16
./midi.py attack 64
./midi.py decay 32
./midi.py sustain 100
./midi.py release 80
./midi.py next                     # next file (CC48)
./midi.py prev                     # previous file (CC47)
./midi.py roboto                   # toggle roboto effect
./midi.py whisper                  # toggle whisper effect
./midi.py alien                    # toggle alien effect

Options

Option	Description
--port, -p	amidi port (default: hw:4,0)
--channel, -c	MIDI channel 0–15 (default: 0)
--list, -l	List available MIDI ports and exit
--connect	Connect VirMIDI → Cloudbuster and exit