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fjroland

Pronounced /fērōland, fyrōland/ - A multifunction drum sequencer, written in Go.

Features

  • Command line based rendering of sequencer timeline in real time
  • Pattern files are easily editable in plain text
  • Sequencer watches for pattern file changes to allow interactive editing of patterns
  • Sequencer can output audio via .wav file sample packs
  • Sequencer can output midi to play pattern a midi device
  • Example patterns and sample packs are included to play with. (Sorry, you have to buy your own midi device)

Building

fjrolad was developed and tested with go 1.15 on OS X 10.15.

Before building the binary make sure you have the devlopment libraries for portmidi, portaudio and libsndfile installed. On OS X with Homebrew configure you can do that with this command:

brew install portmidi portaudio libsndfile

After you have the development libraries installed, make build in the root directory will build the binary and store it as bin/fjroland.

Running

Usage:
  fjroland [OPTIONS] PatternFile

Application Options:
  -m, --midi=        A midi device name to output to
  -s, --samples=     A directory of samples to use for waveform playback

Help Options:
  -h, --help         Show this help message

There are exmaple pattern files in assets/patterns/ and a couple of sample packs in assets/samplepacks. Try this command to play "Vivrant Thing" on an accoustic drum set:

bin/fjroland assets/patterns/vivrant-thing.json -s assets/samplepacks/acoustic/

Or, you can try a TR-909:

bin/fjroland assets/patterns/vivrant-thing.json -s assets/samplepacks/909/

Pattern File Format

The pattern file is a json document - it's easily parsed in any language, human readable, and easily editable. When you start the sequencer for a pattern, the sequencer watches for changes in the file and hot-reloads the pattern so you can play with patterns and hear the chnages interactively.

The pattern file has three fields:

  • title - The title of the pattern being played
  • bpm - The tempo of the pattern, in beats per minute

Each track takes the form of:

Instrument Name: timeline

The instrument names are standard names, but their spellings are important as the instrument name is how the samples or midi codes are generated. They are case-insensitive though.

The timeline is a |-separated set of markers can be any length. Each | represents a beat. The other markers are as follows:

  • o - Ghost note
  • X - Standard note
  • > - Accented note

While timelines can be any length, they must conform to the following rules or they will will not be valid:

  • Each beat in a timeline must have the same number of divisions
  • All timelines must have the same number of beats and divisions

The following is a simple "Four on the Floor" pattern. It's 4 beats, divided into 4 divisions per beat.

{
    "title": "Four on the Floor",
    "bpm": 100,
    "tracks": [
    "Snare:         |----|X---|----|X---|",
    "Closed Hi-Hat: |X-X-|X-X-|X-X-|X-X-|",
    "Bass:          |X---|X---|X---|X---|"
    ]
}

Here is a more sophisticated example - the rythm for "Don't Say Nuthin'" by The Roots. This also has 4 divisisons per beat, but the pattern has 8 beats since it's a two bar phrase. You can also see it uses accent notes (>).

{
    "title": "Don't Say Nothin' - The Roots",
    "bpm": 99,
    "tracks": [
    "Closed Hi-Hat: |X-X-|X-X-|X-X-|X-X-|X-X-|X-X-|X-X-|X-X-|",
    "Snare:         |----|>---|----|>---|----|>---|----|>---|",
    "Bass:          |X---|----|--X-|-X--|X---|----|----|-X--|"
    ]
}

Finally, here is the pattern for the intro to "Turn Down for What" by DJ Snake and Lil Jon. It's only 4 beats long, but each beat is broken down into 8 divisions to accomodate the the 32nd notes in the final beat.

{
    "title": "Turn Down for What (Intro)- DJ Snake, Lil Jon",
    "bpm": 100,
    "tracks": [
    "Snare: |>-X-X->-|X-X->-X-|X->-X-X-|>->->>>>|"
    ]
}

Sample Packs

Sample packs are just directories of properly named wav files. This is the listing of the assets/samples/acoustic directory:

assets/samplepacks/acoustic/
├── Bass.wav
├── Closed Hi-Hat.wav
├── Crash Cymbal.wav
├── Cross-stick.wav
├── High Tom.wav
├── Low Tom.wav
├── Open Hi-Hat.wav
├── Pedal Hi-Hat.wav
├── Rimshot.wav
└── Snare.wav

Sample files must be wav files in stereo, sampled at 44.1k.

Midi Devices

You can also output you pattern to an eligible midi device. This has been tested against the Alesis SamplePad4.

To output to a midi device pass the name of the device, as it's identified to the host system, via the -m command line option. e.g.:

bin/fjroland assets/patterns/vivrant-thing.json -m SamplePad