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juce::Synthesiser Class Reference

## Detailed Description

Base class for a musical device that can play sounds.

To create a synthesiser, you'll need to create a subclass of SynthesiserSound to describe each sound available to your synth, and a subclass of SynthesiserVoice which can play back one of these sounds.

Then you can use the addVoice() and addSound() methods to give the synthesiser a set of sounds, and a set of voices it can use to play them. If you only give it one voice it will be monophonic - the more voices it has, the more polyphony it'll have available.

Then repeatedly call the renderNextBlock() method to produce the audio. Any midi events that go in will be scanned for note on/off messages, and these are used to start and stop the voices playing the appropriate sounds.

While it's playing, you can also cause notes to be triggered by calling the noteOn(), noteOff() and other controller methods.

Before rendering, be sure to call the setCurrentPlaybackSampleRate() to tell it what the target playback rate is. This value is passed on to the voices so that they can pitch their output correctly.

The documentation for this class was generated from the following file:

- juce_audio_basics/synthesisers/juce_Synthesiser.h

## Public Member Functions

| Synthesiser ()
| Creates a new synthesiser.
virtual | ~Synthesiser ()
| Destructor.
void | clearVoices ()
| Deletes all voices.
int | getNumVoices () const noexcept
| Returns the number of voices that have been added.
SynthesiserVoice * | getVoice (int index) const
| Returns one of the voices that have been added.
SynthesiserVoice * | addVoice (SynthesiserVoice *newVoice)
| Adds a new voice to the synth.
void | removeVoice (int index)
| Deletes one of the voices.
void | clearSounds ()
| Deletes all sounds.
int | getNumSounds () const noexcept
| Returns the number of sounds that have been added to the synth.
SynthesiserSound::Ptr | getSound (int index) const noexcept
| Returns one of the sounds.
SynthesiserSound * | addSound (const SynthesiserSound::Ptr &newSound)
| Adds a new sound to the synthesiser.
void | removeSound (int index)
| Removes and deletes one of the sounds.
void | setNoteStealingEnabled (bool shouldStealNotes)
| If set to true, then the synth will try to take over an existing voice if it runs out and needs to play another note.
bool | isNoteStealingEnabled () const noexcept
| Returns true if note-stealing is enabled.
virtual void | noteOn (int midiChannel, int midiNoteNumber, float velocity)
| Triggers a note-on event.
virtual void | noteOff (int midiChannel, int midiNoteNumber, float velocity, bool allowTailOff)
| Triggers a note-off event.
virtual void | allNotesOff (int midiChannel, bool allowTailOff)
| Turns off all notes.
virtual void | handlePitchWheel (int midiChannel, int wheelValue)
| Sends a pitch-wheel message to any active voices.
virtual void | handleController (int midiChannel, int controllerNumber, int controllerValue)
| Sends a midi controller message to any active voices.
virtual void | handleAftertouch (int midiChannel, int midiNoteNumber, int aftertouchValue)
| Sends an aftertouch message.
virtual void | handleChannelPressure (int midiChannel, int channelPressureValue)
| Sends a channel pressure message.
virtual void | handleSustainPedal (int midiChannel, bool isDown)
| Handles a sustain pedal event.
virtual void | handleSostenutoPedal (int midiChannel, bool isDown)
| Handles a sostenuto pedal event.
virtual void | handleSoftPedal (int midiChannel, bool isDown)
| Can be overridden to handle soft pedal events.
virtual void | handleProgramChange (int midiChannel, int programNumber)
| Can be overridden to handle an incoming program change message.
virtual void | setCurrentPlaybackSampleRate (double sampleRate)
| Tells the synthesiser what the sample rate is for the audio it's being used to render.
void | renderNextBlock (AudioBuffer< float > &outputAudio, const MidiBuffer &inputMidi, int startSample, int numSamples)
| Creates the next block of audio output.
void | renderNextBlock (AudioBuffer< double > &outputAudio, const MidiBuffer &inputMidi, int startSample, int numSamples)
double | getSampleRate () const noexcept
| Returns the current target sample rate at which rendering is being done.
void | setMinimumRenderingSubdivisionSize (int numSamples, bool shouldBeStrict=false) noexcept
| Sets a minimum limit on the size to which audio sub-blocks will be divided when rendering.

## Protected Member Functions

virtual void | renderVoices (AudioBuffer< float > &outputAudio, int startSample, int numSamples)
| Renders the voices for the given range.
virtual void | renderVoices (AudioBuffer< double > &outputAudio, int startSample, int numSamples)
virtual SynthesiserVoice * | findFreeVoice (SynthesiserSound *soundToPlay, int midiChannel, int midiNoteNumber, bool stealIfNoneAvailable) const
| Searches through the voices to find one that's not currently playing, and which can play the given sound.
virtual SynthesiserVoice * | findVoiceToSteal (SynthesiserSound *soundToPlay, int midiChannel, int midiNoteNumber) const
| Chooses a voice that is most suitable for being re-used.
void | startVoice (SynthesiserVoice *voice, SynthesiserSound *sound, int midiChannel, int midiNoteNumber, float velocity)
| Starts a specified voice playing a particular sound.
void | stopVoice (SynthesiserVoice *, float velocity, bool allowTailOff)
| Stops a given voice.
virtual void | handleMidiEvent (const MidiMessage &)
| Can be overridden to do custom handling of incoming midi events.

## Protected Attributes

CriticalSection | lock
| This is used to control access to the rendering callback and the note trigger methods.
OwnedArray< SynthesiserVoice > | voices
ReferenceCountedArray< SynthesiserSound > | sounds
int | lastPitchWheelValues [16]
| The last pitch-wheel values for each midi channel.

## Constructors and Destructors

## Synthesiser()

juce::Synthesiser::Synthesiser | ( |  | ) |

Creates a new synthesiser.

You'll need to add some sounds and voices before it'll make any sound.

Referenced by handleMidiEvent().

## ~Synthesiser()

virtual juce::Synthesiser::~Synthesiser | ( |  | ) |

virtual

Destructor.

## Member Functions

## clearVoices()

void juce::Synthesiser::clearVoices | ( |  | ) |

Deletes all voices.

## getNumVoices()

int juce::Synthesiser::getNumVoices | ( |  | ) | const

inline noexcept

Returns the number of voices that have been added.

References voices.

## getVoice()

SynthesiserVoice * juce::Synthesiser::getVoice | ( | int | index | ) | const

Returns one of the voices that have been added.

## addVoice()

SynthesiserVoice * juce::Synthesiser::addVoice | ( | SynthesiserVoice * | newVoice | ) |

Adds a new voice to the synth.

All the voices should be the same class of object and are treated equally.

The object passed in will be managed by the synthesiser, which will delete it later on when no longer needed. The caller should not retain a pointer to the voice.

## removeVoice()

void juce::Synthesiser::removeVoice | ( | int | index | ) |

Deletes one of the voices.

## clearSounds()

void juce::Synthesiser::clearSounds | ( |  | ) |

Deletes all sounds.

## getNumSounds()

int juce::Synthesiser::getNumSounds | ( |  | ) | const

inline noexcept

Returns the number of sounds that have been added to the synth.

References sounds.

## getSound()

SynthesiserSound::Ptr juce::Synthesiser::getSound | ( | int | index | ) | const

inline noexcept

Returns one of the sounds.

References sounds.

## addSound()

SynthesiserSound * juce::Synthesiser::addSound | ( | const SynthesiserSound::Ptr & | newSound | ) |

Adds a new sound to the synthesiser.

The object passed in is reference counted, so will be deleted when the synthesiser and all voices are no longer using it.

## removeSound()

void juce::Synthesiser::removeSound | ( | int | index | ) |

Removes and deletes one of the sounds.

## setNoteStealingEnabled()

void juce::Synthesiser::setNoteStealingEnabled | ( | bool | shouldStealNotes | ) |

If set to true, then the synth will try to take over an existing voice if it runs out and needs to play another note.

The value of this boolean is passed into findFreeVoice(), so the result will depend on the implementation of this method.

## isNoteStealingEnabled()

bool juce::Synthesiser::isNoteStealingEnabled | ( |  | ) | const

inline noexcept

Returns true if note-stealing is enabled.

See also
  setNoteStealingEnabled

## noteOn()

virtual void juce::Synthesiser::noteOn | ( | int | midiChannel,
|  | int | midiNoteNumber,
|  | float | velocity )

virtual

Triggers a note-on event.

The default method here will find all the sounds that want to be triggered by this note/channel. For each sound, it'll try to find a free voice, and use the voice to start playing the sound.

Subclasses might want to override this if they need a more complex algorithm.

This method will be called automatically according to the midi data passed into renderNextBlock(), but may be called explicitly too.

The midiChannel parameter is the channel, between 1 and 16 inclusive.

## noteOff()

virtual void juce::Synthesiser::noteOff | ( | int | midiChannel,
|  | int | midiNoteNumber,
|  | float | velocity,
|  | bool | allowTailOff )

virtual

Triggers a note-off event.

This will turn off any voices that are playing a sound for the given note/channel.

If allowTailOff is true, the voices will be allowed to fade out the notes gracefully (if they can do). If this is false, the notes will all be cut off immediately.

This method will be called automatically according to the midi data passed into renderNextBlock(), but may be called explicitly too.

The midiChannel parameter is the channel, between 1 and 16 inclusive.

## allNotesOff()

virtual void juce::Synthesiser::allNotesOff | ( | int | midiChannel,
|  | bool | allowTailOff )

virtual

Turns off all notes.

This will turn off any voices that are playing a sound on the given midi channel.

If midiChannel is 0 or less, then all voices will be turned off, regardless of which channel they're playing. Otherwise it represents a valid midi channel, from 1 to 16 inclusive.

If allowTailOff is true, the voices will be allowed to fade out the notes gracefully (if they can do). If this is false, the notes will all be cut off immediately.

This method will be called automatically according to the midi data passed into renderNextBlock(), but may be called explicitly too.

## handlePitchWheel()

virtual void juce::Synthesiser::handlePitchWheel | ( | int | midiChannel,
|  | int | wheelValue )

virtual

Sends a pitch-wheel message to any active voices.

This will send a pitch-wheel message to any voices that are playing sounds on the given midi channel.

This method will be called automatically according to the midi data passed into renderNextBlock(), but may be called explicitly too.

Parameters

  midiChannel | the midi channel, from 1 to 16 inclusive
  wheelValue | the wheel position, from 0 to 0x3fff, as returned by MidiMessage::getPitchWheelValue()

## handleController()

virtual void juce::Synthesiser::handleController | ( | int | midiChannel,
|  | int | controllerNumber,
|  | int | controllerValue )

virtual

Sends a midi controller message to any active voices.

This will send a midi controller message to any voices that are playing sounds on the given midi channel.

This method will be called automatically according to the midi data passed into renderNextBlock(), but may be called explicitly too.

Parameters

  midiChannel | the midi channel, from 1 to 16 inclusive
  controllerNumber | the midi controller type, as returned by MidiMessage::getControllerNumber()
  controllerValue | the midi controller value, between 0 and 127, as returned by MidiMessage::getControllerValue()

## handleAftertouch()

virtual void juce::Synthesiser::handleAftertouch | ( | int | midiChannel,
|  | int | midiNoteNumber,
|  | int | aftertouchValue )

virtual

Sends an aftertouch message.

This will send an aftertouch message to any voices that are playing sounds on the given midi channel and note number.

This method will be called automatically according to the midi data passed into renderNextBlock(), but may be called explicitly too.

Parameters

  midiChannel | the midi channel, from 1 to 16 inclusive
  midiNoteNumber | the midi note number, 0 to 127
  aftertouchValue | the aftertouch value, between 0 and 127, as returned by MidiMessage::getAftertouchValue()

## handleChannelPressure()

virtual void juce::Synthesiser::handleChannelPressure | ( | int | midiChannel,
|  | int | channelPressureValue )

virtual

Sends a channel pressure message.

This will send a channel pressure message to any voices that are playing sounds on the given midi channel.

This method will be called automatically according to the midi data passed into renderNextBlock(), but may be called explicitly too.

Parameters

  midiChannel | the midi channel, from 1 to 16 inclusive
  channelPressureValue | the pressure value, between 0 and 127, as returned by MidiMessage::getChannelPressureValue()

## handleSustainPedal()

virtual void juce::Synthesiser::handleSustainPedal | ( | int | midiChannel,
|  | bool | isDown )

virtual

Handles a sustain pedal event.

## handleSostenutoPedal()

virtual void juce::Synthesiser::handleSostenutoPedal | ( | int | midiChannel,
|  | bool | isDown )

virtual

Handles a sostenuto pedal event.

## handleSoftPedal()

virtual void juce::Synthesiser::handleSoftPedal | ( | int | midiChannel,
|  | bool | isDown )

virtual

Can be overridden to handle soft pedal events.

## handleProgramChange()

virtual void juce::Synthesiser::handleProgramChange | ( | int | midiChannel,
|  | int | programNumber )

virtual

Can be overridden to handle an incoming program change message.

The base class implementation of this has no effect, but you may want to make your own synth react to program changes.

## setCurrentPlaybackSampleRate()

virtual void juce::Synthesiser::setCurrentPlaybackSampleRate | ( | double | sampleRate | ) |

virtual

Tells the synthesiser what the sample rate is for the audio it's being used to render.

This value is propagated to the voices so that they can use it to render the correct pitches.

## renderNextBlock() [1/2]

void juce::Synthesiser::renderNextBlock | ( | AudioBuffer< float > & | outputAudio,
|  | const MidiBuffer & | inputMidi,
|  | int | startSample,
|  | int | numSamples )

Creates the next block of audio output.

This will process the next numSamples of data from all the voices, and add that output to the audio block supplied, starting from the offset specified. Note that the data will be added to the current contents of the buffer, so you should clear it before calling this method if necessary.

The midi events in the inputMidi buffer are parsed for note and controller events, and these are used to trigger the voices. Note that the startSample offset applies both to the audio output buffer and the midi input buffer, so any midi events with timestamps outside the specified region will be ignored.

## renderNextBlock() [2/2]

void juce::Synthesiser::renderNextBlock | ( | AudioBuffer< double > & | outputAudio,
|  | const MidiBuffer & | inputMidi,
|  | int | startSample,
|  | int | numSamples )

## getSampleRate()

double juce::Synthesiser::getSampleRate | ( |  | ) | const

inline noexcept

Returns the current target sample rate at which rendering is being done.

Subclasses may need to know this so that they can pitch things correctly.

## setMinimumRenderingSubdivisionSize()

void juce::Synthesiser::setMinimumRenderingSubdivisionSize | ( | int | numSamples,
|  | bool | shouldBeStrict = false )

noexcept

Sets a minimum limit on the size to which audio sub-blocks will be divided when rendering.

When rendering, the audio blocks that are passed into renderNextBlock() will be split up into smaller blocks that lie between all the incoming midi messages, and it is these smaller sub-blocks that are rendered with multiple calls to renderVoices().

Obviously in a pathological case where there are midi messages on every sample, then renderVoices() could be called once per sample and lead to poor performance, so this setting allows you to set a lower limit on the block size.

The default setting is 32, which means that midi messages are accurate to about < 1ms accuracy, which is probably fine for most purposes, but you may want to increase or decrease this value for your synth.

If shouldBeStrict is true, the audio sub-blocks will strictly never be smaller than numSamples.

If shouldBeStrict is false (default), the first audio sub-block in the buffer is allowed to be smaller, to make sure that the first MIDI event in a buffer will always be sample-accurate (this can sometimes help to avoid quantisation or phasing issues).

## renderVoices() [1/2]

virtual void juce::Synthesiser::renderVoices | ( | AudioBuffer< float > & | outputAudio,
|  | int | startSample,
|  | int | numSamples )

protected virtual

Renders the voices for the given range.

By default this just calls renderNextBlock() on each voice, but you may need to override it to handle custom cases.

References renderVoices().

Referenced by renderVoices(), and renderVoices().

## renderVoices() [2/2]

virtual void juce::Synthesiser::renderVoices | ( | AudioBuffer< double > & | outputAudio,
|  | int | startSample,
|  | int | numSamples )

protected virtual

References renderVoices().

## findFreeVoice()

virtual SynthesiserVoice * juce::Synthesiser::findFreeVoice | ( | SynthesiserSound * | soundToPlay,
|  | int | midiChannel,
|  | int | midiNoteNumber,
|  | bool | stealIfNoneAvailable ) const

protected virtual

Searches through the voices to find one that's not currently playing, and which can play the given sound.

Returns nullptr if all voices are busy and stealing isn't enabled.

To implement a custom note-stealing algorithm, you can either override this method, or (preferably) override findVoiceToSteal().

References findFreeVoice().

Referenced by findFreeVoice().

## findVoiceToSteal()

virtual SynthesiserVoice * juce::Synthesiser::findVoiceToSteal | ( | SynthesiserSound * | soundToPlay,
|  | int | midiChannel,
|  | int | midiNoteNumber ) const

protected virtual

Chooses a voice that is most suitable for being re-used.

The default method will attempt to find the oldest voice that isn't the bottom or top note being played. If that's not suitable for your synth, you can override this method and do something more cunning instead.

References findVoiceToSteal().

Referenced by findVoiceToSteal().

## startVoice()

void juce::Synthesiser::startVoice | ( | SynthesiserVoice * | voice,
|  | SynthesiserSound * | sound,
|  | int | midiChannel,
|  | int | midiNoteNumber,
|  | float | velocity )

protected

Starts a specified voice playing a particular sound.

You'll probably never need to call this, it's used internally by noteOn(), but may be needed by subclasses for custom behaviours.

References startVoice().

Referenced by startVoice().

## stopVoice()

void juce::Synthesiser::stopVoice | ( | SynthesiserVoice * | ,
|  | float | velocity,
|  | bool | allowTailOff )

protected

Stops a given voice.

You should never need to call this, it's used internally by noteOff, but is protected in case it's useful for some custom subclasses. It basically just calls through to SynthesiserVoice::stopNote(), and has some assertions to sanity-check a few things.

References stopVoice().

Referenced by stopVoice().

## handleMidiEvent()

virtual void juce::Synthesiser::handleMidiEvent | ( | const MidiMessage & |  | ) |

protected virtual

Can be overridden to do custom handling of incoming midi events.

References handleMidiEvent(), JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR, and Synthesiser().

Referenced by handleMidiEvent().

## Member Data Documentation

## lock

CriticalSection juce::Synthesiser::lock

protected

This is used to control access to the rendering callback and the note trigger methods.

## voices

OwnedArray<SynthesiserVoice> juce::Synthesiser::voices

protected

Referenced by getNumVoices().

## sounds

ReferenceCountedArray<SynthesiserSound> juce::Synthesiser::sounds

protected

Referenced by getNumSounds(), and getSound().

## lastPitchWheelValues

int juce::Synthesiser::lastPitchWheelValues[16]

protected

The last pitch-wheel values for each midi channel.

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