An Introduction to MIDI Programming with

The Java Sound API : Overview

Provides low level services for digital audio and midi processing.Is essentially an abstraction layer over the lower level native services offered by the operating system.Is hardware agnostic and relies on the operating system to provide access to hardware resources. The Java Sound packages were designed to provide application programmers with a consistent interface to resources and services regardless of the audio hardware configuration.

The Java Sound API : Packages

Two main packages targeted by application programmers

javax.sound.sampled provides services for capturing, mixing, and playback of digital audio streams.javax.sound.midi provides services to support MIDI synthesis, sequencing, and event capture/playback.

The Java Sound API : Packages

Two extension packages for use by system programmers to extend the Java Sound API

javax.sound.sampled.spijavax.sound.midi.spi

Devices, Transmitters, and Receivers

MIDI Devices must be a transmitter, a receiver, or both a transmitter and a receiver.A transmitter is capable of generating MIDI messages.A receiver is capable of capturing MIDI messages.

Devices, Transmitters, and Receivers

A Controller is a MIDI device which generates MIDI messages (Transmitter).A Synthesizer (Software or Hardware) is a MIDI device which captures MIDI messages (Receiver).A Sequencer is a MIDI device which generates and captures MIDI messages (Transmitter and Receiver).

Devices, Transmitters, and Receivers

Transmitters generate MIDI messages and stream them to connected receivers.

MIDI Streaming vs. SequencingStreaming Real Time Processing

MessagesMessage TypeChannel NumberAssociated Data

Sequencing Relative Time Processing

EventsMessage TypeChannel NumberAssociated DataRelative Time

MIDI Streaming

Can be thought of as Live MIDIMIDI Messages contain no timing information and are processed immediately as they arrive.Examples:

A MIDI controller generates MIDI messages which are streamed to capture devices (like sequencers) during recording or sound generators (like synthesizers) during performance.A MIDI sequencer generates MIDI messages which are streamed to devices which generate sound (like synthesizers) during playback.

MIDI Sequencing

Can be thought of as Scheduled MIDI.MIDI Events contain MIDI Messages and associated timing values.Examples:

Playback - A MIDI file stores a series of MIDI Events which a sequencer can use to generate MIDI messages to send to sound generating devices at the appropriate time.Capture - A MIDI sequencer captures MIDI messages from a MIDI controller and adds a time stamp to the message data for storage and subsequent playback.

MIDI Data Flow Sequences and Tracks

Sequence stored in a MIDI File or managed by a MIDI Sequencer.

A Sequence can be thought of as a MIDI schedule.

Track represents a MIDI Event schedule for a single instrument/performer/voice.

Sequences and Tracks

A sequence can be thought of as an entire song, whereas a track can be thought of as a single part of the song like the guitar partor the drum part.

A sequence can, but does not necessarily have to, contain multiple tracks.

Sequences and Tracks

A Sequence is a collection of Tracks

A Track is a collection of MIDI Events

A MIDI Event is a MIDI Message combined with timing information.

MidiDevice Interface

Interface implemented by software representations of MIDI devices.

Can represent both software devices and hardware devices.

Implementations provide all functionality required by a MIDI port (input or output).

MidiDevice Interface

open(), close(), isOpen()

getDeviceInfo()

getReceiver(), getReceivers(), getMaxReceivers()

getTransmitter(), getTransmitters(), getMaxTransmitters()

getMicrosecondPosition()

MidiDevice.Info Class

A data access class whose sole responsibility is to provide information describing a MidiDevice instance.

Clients of a MidiDevice may obtain an instance of this class to query for information about the MidiDevice by calling the MidiDevices getDeviceInfo() method.

MidiDevice.Info Class

getName()

getVendor()

getVersion()

getDescription()

Transmitter Interface

Interface implemented by software objects that transmit MIDI messages on behalf of a MidiDevice implementation.

Examples: Sequencers and MIDI Input Ports provide Transmitters to clients.

Transmitter Interface

Instances of a MidiDevices Transmitter implementation can be obtained by calling the MidiDevices getTransmitter() method.

Be sure to call the Transmitter instances close() method when the Transmitter is no longer needed.

Transmitter Interface

setReceiver(), getReceiver()

close()

Receiver Interface

Interface implemented by software objects that receive MIDI messages on behalf of a MidiDevice implementation.

Examples: Synthesizers and MIDI Output Ports provide Receivers to clients.

Receiver Interface

Instances of a MidiDevices Receiver implementation can be obtained by calling the MidiDevices getReceiver() method.

Be sure to call the Receiver instances close() method when the Receiver is no longer needed.

Receiver Interface

send()

close()

MidiMessage Class

Base class for all MIDI Message implementations.

Provides access to the messages status byte, data bytes, and total message length.

Subclasses include ShortMessage, MetaMessage, and SysExMessage classes.

MidiMessage Class

getStatus()

getLength()

getMessage()

ShortMessage Class

Implements data access and transport for short messages (2 data bytes) which are usually associated with MIDI channels.

Examples: Note On and Note Off messages

ShortMessage Class

getCommand()

getChannel()

getData1(), getData2()

getDataLength()

setMessage()

ShortMessage Class

Status code byte values are provided by static fields on the ShortMessage class.

Examples:ShortMessage.NOTE_ONShortMessage.NOTE_OFFShortMessage.PITCH_BEND

SysexMessage Class

Implements data access and transport for MIDI system exclusive messages.

MIDI system exclusive messages are largely vendor specific and are variable in size.

SysexMessage Class

getData()

setMessage()

MetaMessage Class

Implements data access and transport for MIDI meta messages.

MetaMessages are used in MIDI files and Sequences and are not used during live communication.

Contain data useful for sequencers like tempo changes, time signatures, etc.

MetaMessage Class

getType()

getData()

setMessage()

Sequence Interface

Extends the MidiDevice Interface

Implemented by classes which represent MIDI Sequencers.

Sequencer Interface

getSequence(), setSequence()

getTickLength()

getTickPosition(), setTickPosition()

start(), stop()

Sequencer Interface

startRecording(), stopRecording()

isRunning(), isRecording()

getTrackSolo(), setTrackSolo()

getTrackMute(), setTrackMute()

Sequencer Interface

addControllerEventListener()

addMetaEventListener()

Sequence Class

Implements data access and manipulation for a MIDI Sequence.

Is essentially a collection of Track objects and provides the ability to add, access, and remove Tracks.

Sequence Class

createTrack(), deleteTrack()

getTracks()

getTickLength()

Track Class

Implements an ordered collection of MidiEvent objects.

Represents the MIDI message schedule for a single instrument or voice for a Sequence.

Tracks can only be created by calling a Sequences createTrack() method.

Track Class

add(), remove()

get()

size()

ticks()

MidiEvent Class

Implements data access and transport for a MIDI Event.

Is, quite simply, a container for a MidiMessage object and an associated tick value.

MidiEvent Class

getTick(), setTick()

getMessage()

Event Listener Interfaces

ControllerEventListener InterfacecontrolChange()

MetaEventListener Interfacemeta()

Synthesizer Interface

Extends the MidiDevice Interface

Implemented by software objects that represent MIDI Synthesizers.

Implementations of this interface are the only objects in the Midi package that produce audio.

Synthesizer Interface

getChannels()

getAvailableInstruments()

getMaxPolyphony()

getLatency()

getVoiceStatus()

Instrument Class

Implements the sound synthesis algorithms for a specific instrument provided by a Soundbank.

To use an instance of an Instrument object with a Synthesizer, that Instrument and its Soundbank must be loaded into the Synthesizer.

Instrument Class

getName()

getPatch()

Patch Class

Implementation of an Instruments sound patch.

Represents the location at which an instruments data is loaded into a synthesizer.

Provides the bank and program numbers to a MidiChannel so the channel can use the instrument.

Patch Class

getBank()

getProgram()

MidiChannel Interface

Interface for implementations of a MIDI Channel provided by a Synthesizer.

Instances can be retrieved by calling a Synthesizer instances getChannels() method.

Synthesizers usually provide 16 MidiChannel instances to clients.

MidiChannel Interface

noteOn(), noteOff()

allNotesOff()

controlChange(), getController()

getPitchBend(), setPitchBend()

MidiChannel Interface

getSolo(), setSolo()

getMute(), setMute()

getProgram(), programChange()

MidiSystem Class

Provides access to the systems MIDI resources (installed hardware and software based MIDI devices, soundbanks, etc.)

Like most subsystems in the Java Libraries, the MIDI subsystem is implemented as a Singleton by exposing only static methods.

MidiSystem Class

getMidiDeviceInfo()

getMidiDevice()

getReceiver(), getTransmitter(), getSynthesizer(), getSequencer()

getSequence()

MidiSystem Class

getMidiFileTypes()

write()

References

JavaSound API Programmers Guidehttp://download.oracle.com/javase/1.5.0/docs/guide/sound/programmer_guide/index.html

Java SE 6 APIhttp://download.oracle.com/javase/6/docs/api/javax/sound/midi/package-summary.html

Java Sound API Soundbankshttp://www.oracle.com/technetwork/java/soundbanks-135798.html