grainman

Interactive granular synthesizer

This is a command line program implementing granular synthesis . It works by playing many (very many) short, randomized samples from an audio file, called grains. This creates some pretty cool sounds even from very simple inputs.

Here is an example of what it can sound like:

The program uses Jack as a backend and is primarily controlled through its command line interface. A full list of commands can be displayed with the help command. There are commands for importing samples, creating profiles and connecting to audio ports, as well as for changing attributes that control how the synthesizer works. If you're interested in trying this program, I've written a brief guide below. Here are instructions for building and installing grainman.

Creating samples and synthesizer profiles

To import an audio file for sampling:

 import-sample <sample name> <path>

To create a new synthesizer profile:

 add-profile <profile name> <sample name>

To start synthesizeing, run:

start

Controlling the synthesizer

Different profiles have different attributes that control how the audio is synthesized. The command for updating an attribute is

 set-attribute <profile name> <attribute name> <value>

Synthesizer attributes

• Number of grain slots, num-slots
  This controls how many grains are "active" at the same time, meaning it's an upper limit of the number of samples played simultaneously.
• Minimum/maximum length of grains, min-length/max-length
  The length in seconds of each sample. Very short grains usually results in noisy audio. As for all min-max parameters, the length is randomized for each grain.
• Minimum/maximum gain, min-gain/max-gain
  Randomized gain for each played sample.
• Minimum/maximum cooldown time, min-cooldown/max-cooldown
  Specifies a "cooldown" for each grain after it finishes playing. Short lengths and long cooldown times give a nice crackle.
• Minimum/maximum multiplier, min-multiplier/max-multiplier
  The "multiplier" specifies the factor with which a sample may be sped up/slowed down. This is how pitch is controlled.
• Reverse probability, reverse-probability
  Specifies a probability between 0 and 1 for an individual sample to be reversed.

Using MIDI devices

It is possible to connect to MIDI input devices, for controlling synthesizer attributes. To connect to a device, use the following command:

 add-midi-device <name> <pattern matching a port name in Jack>

To connect a MIDI control change message to a specific attribute:

map-midi-cc <device name> <CC function> <profile name> <attribute name> <min> <max>

This will map the interval 0-127 to [<min>, <max>].

It is also possible to clamp the multiplier attribute to the nearest pitch played on a MIDI keyboard:

map-midi <device name> <profile name>
set-attribute <profile name> use-pitches yes

Note that it doesn't matter in which octave a note is played, the register is based on min-multiplier and max-multiplier.

You can map a control change function to "locking" the pitches. I've used this to play a chord on the keyboard, keep it sustained with the middle pedal, and then improvising with the chord in the background. This can be done like this:

map-lock-toggle <device name> <CC function> <profile>

"Scripting"

Having to type in the commands to the set things up every time you want to use the program is not very nice. There is a source command that will read commands from a file:

source <path>

There is a special rule for files with the extension .sh: in this case, instead of reading commands directly from the file, a child process running bash interprets the file and the commands are read from the child processes standard output. Note: only source scripts that you trust.

Here is an example script:

#! /usr/bin/env bash

min_gain=0.0
max_gain=1.0
min_multiplier=0.2
max_multiplier=4.0
min_length=0.001
max_length=4.0
min_num_slots=1
max_num_slots=512
min_cooldown=0.0
max_cooldown=1.0

cat <<EOF

# Connect to external MIDI devices
# One will be used to control attributes,
# the other one for pitches

add-midi-device control nanoKONTROL2
add-midi-device keyboard Q49

# Import audio sample and create synthesizer profile

import-sample default-sample sample.wav
add-profile default-profile default-sample

# Set initial values for attributes and map
# control change functions to each one.
# I like to set the initial value to the lower
# limit, and start the program with all sliders at zero.

set-attribute default-profile min-multiplier $min_multiplier
set-attribute default-profile max-multiplier $min_multiplier
map-midi-cc control 0 default-profile min-multiplier $min_multiplier $max_multiplier
map-midi-cc control 1 default-profile max-multiplier $min_multiplier $max_multiplier

set-attribute default-profile min-length $min_length
set-attribute default-profile max-length $min_length
map-midi-cc control 2 default-profile min-length $min_length $max_length
map-midi-cc control 3 default-profile max-length $min_length $max_length

set-attribute default-profile num-slots $min_num_slots
map-midi-cc control 17 default-profile num-slots $min_num_slots $max_num_slots

set-attribute default-profile min-gain $min_gain
set-attribute default-profile max-gain $min_gain
map-midi-cc control 16 default-profile max-gain $min_gain $max_gain

# This one is not controlled by MIDI
set-attribute default-profile min-cooldown $min_cooldown
set-attribute default-profile max-cooldown $max_cooldown

# Snap multiplers to pitches played on keyboard
map-midi keyboard default-profile
set-attribute default-profile use-pitches yes

# Use MIDI controller to lock pitches
map-lock-toggle control 45 feedback

# Start grainman!
start

EOF

Building and installing

Currently, the only supported platform is Linux. You will need pkg-config , libsndfile , libsamplerate and libjack installed. Run the following commands to download, build and install grainman under <prefix>:

curl -LO https://ludviggl.duckdns.org/projects/grainman/grainman.tar.gz
tar -xvf grainman.tar.gz
make -C grainman/
make -C grainman/ install PREFIX=<prefix>