Add a rhythm engine

## hyperlinks to be updated to https://github.com/jjazzboss/JJazzLab instead of deprecated JJazzLab-X

Architecture

The main APIs you'll be using are found in the Rhythm and RhythmMusicGeneration modules:

• RhythmProvider

  Give JJazzLab-X access to one or more Rhythm objects provided by your engine

• Rhythm

  The main interface which provides descriptive information about the rhythm, with its RhythmVoices, and hythmParameters.

• MusicGenerator A Rhythm implementation should also implement the MusicGenerator interface to be able to generate music
• RhythmVoice

  There is one RhythmVoice for each track generated by your rhythm, e.g. "Drums", "Bass", "Piano"

• RhythmParameter

  The parameters to modulate the rhythm, e.g. "Complexity" or "Fill"

Create your code

You should first create your own Netbeans module, as explained in the Getting started page.

Your engine must be recognized by the JJazzLab framework, so that it can be accessible to the end-user. For this you'll need to start by adding a RhythmProvider implementation, as explained below.

Main interfaces

RhythmProvider

The RhythmProvider interface is defined in the Rhythm module.

Your implementation must use the @ServiceProvider annotation so that the RhythmDatabase instance can automatically find it upon startup. The general Netbeans mechanism used is described here.

When user needs to pick up a rhythm, the rhythm selection dialog asks the RhythmDatabase to provide the available RhythmProvider instances (e.g. "Yamaha style based generator") and their list of rhythms (e.g. "jazz", "pop", ...).

The RhythmProvider implementation is responsible to provide:

• An Info object (name, description, author, version, uniqueId)

• The list of built-in Rhythm objects provided by this implementation

• The list of file-based Rhythm objects provided by this implementation

• An optional settings dialog to tune the rhythm generation engine

Example: See RhythmStubProviderImpl.java for a simple RhythmProvider implementation example.

Rhythm

A Rhythm interface describes... a rhythm !

• name, for example "samba-fast"

• description

• time signature

• preferred tempo

• feel : ternary/binary

• etc...

It also defines the RhythmVoices, RhythmParameters.

The Rhythm implementation must also implement the MusicGenerator interface to be able to generate music.

Example: See RhythmStub.java for a very simple Rhythm implementation example.

RhythmVoice

There is one RhythmVoice for each track generated by this rhythm, e.g. "Drums", "Bass", "Piano". The RhythmVoiceprovides the recommended Midi instrument and settings for the track.

The RhythmVoices information is used for example by the Mix Console to display the relevant tracks.

RhythmParameter

Examples of RhythmParameters are "Variation", "Fill", or "Complexity".

The RhythmParameters are the control knobs given to the user so he can modulate the rhythm for each song part. You see them in the Song Structure Editor, for each Song Part.

There are ready-to-use classes to quickly define your RhythmParameters depending on their type (a boolean value, one value amongst a set of values, etc). When these classes are used the framework will automatically show the relevant UI widget in the Song Structure Editor. You can also define your own UI widgets if you prefer.

MusicGenerator

This is an interface which indicates the capability to generate rhythm music. It has just a single method which takes the music generation context as a parameter, and returns the musical phrases (one per track) that make the backing track.

When user presses the Play button for a given song, JJazzLab-X will:

• prepare the MusicGenerationContext (e.g. mainly a Song object which contains a ChordLeadSheet and a SongStructure)
• If Rhythm implements the MusicGenerator interface, pass it the context data and ask it to generate the backing track

• wait until the MusicGenerator has finished the music generation

• convert the received music data into a Midi sequence

• play the sequence.

So the MusicGenerator is really where the heavy stuff will be done by your engine. There is no synchronization constraint since JJazzLab will simply block until music generation is complete.

Note that you can use any technology to perform the generation, including non-Java ones. Only the lightweight API that connects to JJazzLab needs to be in Java.

Example: See DummyGenerator.java for a very simple MusicGenerator implementation example.