README.md

go-step-sequencer

A step sequencer implemented in Golang using portaudio and libsndfile wrappers.

Dependencies

This project requires two dependent libraries, both of which are thinly wrapped by a golang libraries. In order for the project to successfully compile, you will need to install the development libraries of both portaudio and libsndfile for your platform. To learn more about how to install the native libraries of these dependencies, please visit their official sites:

• portaudio
• libsndfile

Build

This project is built using a Makefile, which downloads dependencies, runs the go linter, the go vet tool, and finally, builds the go binary.

$ make

Upon a successful build, the binary will exist in the root level directory of this project. You should be able to invoke it locally with the following command:

$ ./go-step-sequencer

Usage

If you haven't built the tool as indicated above, you should be install the utility using the go tool:

$ go get github.com/kellydunn/go-step-sequencer
$ go install github.com/kellydunn/go-step-sequencer

Now you should be able to use the go-step-sequencer utility on the command line. Use the --help flag to get more information on how to use the utility.

$ go-step-sequencer --help
Usage of go-step-sequencer:
  -kit="kits": -kit=path/to/kits
  -pattern="patterns/pattern_1.splice": -pattern=path/to/pattern.splice

The step sequencer was made to take a pattern and a kit as command line flags so that you can swap out different types of kits and patterns. A typical use of the command looks like this:

$ go-step-sequencer --pattern path/to/pattern.splice --kit path/to/kits

The default pattern is found at patterns/pattern_1.splice and the default kit is located at kits/0.808-alpha. Running go-step-sequnencer without specifying a --pattern or a --kit will run the default pattern with the default kit:

$ go-step-sequencer
loaded sample: kits/0.808-alpha/kick.wav
loaded sample: kits/0.808-alpha/snare.wav
loaded sample: kits/0.808-alpha/clap.wav
loaded sample: kits/0.808-alpha/hh-open.wav
loaded sample: kits/0.808-alpha/hh-close.wav
loaded sample: kits/0.808-alpha/cowbell.wav
Saved with HW Version: 0.808-alpha
Tempo: 120
(0) kick        |x---|x---|x---|x---|
(1) snare       |----|x---|----|x---|
(2) clap        |----|x-x-|----|----|
(3) hh-open     |--x-|--x-|x-x-|--x-|
(4) hh-close    |x---|x---|----|x--x|
(5) cowbell     |----|----|--x-|----|

You should be able to hear the drum track out of your speakers now!

Notes

The synchronization protocol for the step sequencer borrows heavily from the MIDI Beat Clock protocol, which uses 24 Pulses Per Quarter note for a specified Tempo. More information on this technique is found here.

The sampler uses a "Playhead" seeking strategy for playback similar to wavetable sythesizers.

For playback, the sampler mixes all of the tracks encoded in the pattern and outputs them into a single Portaudio Stream.