sound/midi/MidiChannel.java

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package javax.sound.midi;

/**
 * A {@code MidiChannel} object represents a single MIDI channel. Generally,
 * each {@code MidiChannel} method processes a like-named MIDI "channel voice"
 * or "channel mode" message as defined by the MIDI specification. However,
 * {@code MidiChannel} adds some "get" methods that retrieve the value most
 * recently set by one of the standard MIDI channel messages. Similarly, methods
 * for per-channel solo and mute have been added.
 * <p>
 * A {@link Synthesizer} object has a collection of {@code MidiChannels},
 * usually one for each of the 16 channels prescribed by the MIDI 1.0
 * specification. The {@code Synthesizer} generates sound when its
 * {@code MidiChannels} receive {@code noteOn} messages.
 * <p>
 * See the MIDI 1.0 Specification for more information about the prescribed
 * behavior of the MIDI channel messages, which are not exhaustively documented
 * here. The specification is titled
 * {@code MIDI Reference: The Complete MIDI 1.0 Detailed Specification}, and is
 * published by the MIDI Manufacturer's Association
 * (<a href = http://www.midi.org>http://www.midi.org</a>).
 * <p>
 * MIDI was originally a protocol for reporting the gestures of a keyboard
 * musician. This genesis is visible in the {@code MidiChannel} API, which
 * preserves such MIDI concepts as key number, key velocity, and key pressure.
 * It should be understood that the MIDI data does not necessarily originate
 * with a keyboard player (the source could be a different kind of musician, or
 * software). Some devices might generate constant values for velocity and
 * pressure, regardless of how the note was performed. Also, the MIDI
 * specification often leaves it up to the synthesizer to use the data in the
 * way the implementor sees fit. For example, velocity data need not always be
 * mapped to volume and/or brightness.
 *
 * @author David Rivas
 * @author Kara Kytle
 * @see Synthesizer#getChannels
 */
public interface MidiChannel {

    /**
     * Starts the specified note sounding. The key-down velocity usually
     * controls the note's volume and/or brightness. If {@code velocity} is
     * zero, this method instead acts like {@link #noteOff(int)}, terminating
     * the note.
     *
     * @param  noteNumber the MIDI note number, from 0 to 127 (60 = Middle C)
     * @param  velocity the speed with which the key was depressed
     * @see #noteOff(int, int)
     */
    void noteOn(int noteNumber, int velocity);

    /**
     * Turns the specified note off. The key-up velocity, if not ignored, can be
     * used to affect how quickly the note decays. In any case, the note might
     * not die away instantaneously; its decay rate is determined by the
     * internals of the {@code Instrument}. If the Hold Pedal (a controller; see
     * {@link #controlChange(int, int) controlChange}) is down, the effect of
     * this method is deferred until the pedal is released.
     *
     * @param  noteNumber the MIDI note number, from 0 to 127 (60 = Middle C)
     * @param  velocity the speed with which the key was released
     * @see #noteOff(int)
     * @see #noteOn
     * @see #allNotesOff
     * @see #allSoundOff
     */
    void noteOff(int noteNumber, int velocity);

    /**
     * Turns the specified note off.
     *
     * @param  noteNumber the MIDI note number, from 0 to 127 (60 = Middle C)
     * @see #noteOff(int, int)
     */
    void noteOff(int noteNumber);

    /**
     * Reacts to a change in the specified note's key pressure. Polyphonic key
     * pressure allows a keyboard player to press multiple keys simultaneously,
     * each with a different amount of pressure. The pressure, if not ignored,
     * is typically used to vary such features as the volume, brightness, or
     * vibrato of the note.
     * <p>
     * It is possible that the underlying synthesizer does not support this MIDI
     * message. In order to verify that {@code setPolyPressure} was successful,
     * use {@code getPolyPressure}.
     *
     * @param  noteNumber the MIDI note number, from 0 to 127 (60 = Middle C)
     * @param  pressure value for the specified key, from 0 to 127
     *         (127 = maximum pressure)
     * @see #getPolyPressure(int)
     */
    void setPolyPressure(int noteNumber, int pressure);

    /**
     * Obtains the pressure with which the specified key is being depressed.
     * <p>
     * If the device does not support setting poly pressure, this method always
     * returns 0. Calling {@code setPolyPressure} will have no effect then.
     *
     * @param  noteNumber the MIDI note number, from 0 to 127 (60 = Middle C)
     * @return the amount of pressure for that note, from 0 to 127
     *         (127 = maximum pressure)
     * @see #setPolyPressure(int, int)
     */
    int getPolyPressure(int noteNumber);

    /**
     * Reacts to a change in the keyboard pressure. Channel pressure indicates
     * how hard the keyboard player is depressing the entire keyboard. This can
     * be the maximum or average of the per-key pressure-sensor values, as set
     * by {@code setPolyPressure}. More commonly, it is a measurement of a
     * single sensor on a device that doesn't implement polyphonic key pressure.
     * Pressure can be used to control various aspects of the sound, as
     * described under {@link #setPolyPressure(int, int) setPolyPressure}.
     * <p>
     * It is possible that the underlying synthesizer does not support this MIDI
     * message. In order to verify that {@code setChannelPressure} was
     * successful, use {@code getChannelPressure}.
     *
     * @param  pressure the pressure with which the keyboard is being depressed,
     *         from 0 to 127 (127 = maximum pressure)
     * @see #setPolyPressure(int, int)
     * @see #getChannelPressure
     */
    void setChannelPressure(int pressure);

    /**
     * Obtains the channel's keyboard pressure.
     * <p>
     * If the device does not support setting channel pressure, this method
     * always returns 0. Calling {@code setChannelPressure} will have no effect
     * then.
     *
     * @return the amount of pressure for that note, from 0 to 127
     *         (127 = maximum pressure)
     * @see #setChannelPressure(int)
     */
    int getChannelPressure();

    /**
     * Reacts to a change in the specified controller's value. A controller is
     * some control other than a keyboard key, such as a switch, slider, pedal,
     * wheel, or breath-pressure sensor. The MIDI 1.0 Specification provides
     * standard numbers for typical controllers on MIDI devices, and describes
     * the intended effect for some of the controllers. The way in which an
     * {@code Instrument} reacts to a controller change may be specific to the
     * {@code Instrument}.
     * <p>
     * The MIDI 1.0 Specification defines both 7-bit controllers and 14-bit
     * controllers. Continuous controllers, such as wheels and sliders,
     * typically have 14 bits (two MIDI bytes), while discrete controllers, such
     * as switches, typically have 7 bits (one MIDI byte). Refer to the
     * specification to see the expected resolution for each type of control.
     * <p>
     * Controllers 64 through 95 (0x40 - 0x5F) allow 7-bit precision. The value
     * of a 7-bit controller is set completely by the {@code value} argument. An
     * additional set of controllers provide 14-bit precision by using two
     * controller numbers, one for the most significant 7 bits and another for
     * the least significant 7 bits. Controller numbers 0 through 31
     * (0x00 - 0x1F) control the most significant 7 bits of 14-bit controllers;
     * controller numbers 32 through 63 (0x20 - 0x3F) control the least
     * significant 7 bits of these controllers. For example, controller number 7
     * (0x07) controls the upper 7 bits of the channel volume controller, and
     * controller number 39 (0x27) controls the lower 7 bits. The value of a
     * 14-bit controller is determined by the interaction of the two halves.
     * When the most significant 7 bits of a controller are set (using
     * controller numbers 0 through 31), the lower 7 bits are automatically set
     * to 0. The corresponding controller number for the lower 7 bits may then
     * be used to further modulate the controller value.
     * <p>
     * It is possible that the underlying synthesizer does not support a
     * specific controller message. In order to verify that a call to
     * {@code controlChange} was successful, use {@code getController}.
     *
     * @param  controller the controller number (0 to 127; see the MIDI 1.0
     *         Specification for the interpretation)
     * @param  value the value to which the specified controller is changed
     *         (0 to 127)
     * @see #getController(int)
     */
    void controlChange(int controller, int value);

    /**
     * Obtains the current value of the specified controller. The return value
     * is represented with 7 bits. For 14-bit controllers, the MSB and LSB
     * controller value needs to be obtained separately. For example, the 14-bit
     * value of the volume controller can be calculated by multiplying the value
     * of controller 7 (0x07, channel volume MSB) with 128 and adding the value
     * of controller 39 (0x27, channel volume LSB).
     * <p>
     * If the device does not support setting a specific controller, this method
     * returns 0 for that controller. Calling {@code controlChange} will have no
     * effect then.
     *
     * @param  controller the number of the controller whose value is desired.
     *         The allowed range is 0-127; see the MIDI 1.0 Specification for
     *         the interpretation.
     * @return the current value of the specified controller (0 to 127)
     * @see #controlChange(int, int)
     */
    int getController(int controller);

    /**
     * Changes a program (patch). This selects a specific instrument from the
     * currently selected bank of instruments.
     * <p>
     * The MIDI specification does not dictate whether notes that are already
     * sounding should switch to the new instrument (timbre) or continue with
     * their original timbre until terminated by a note-off.
     * <p>
     * The program number is zero-based (expressed from 0 to 127). Note that
     * MIDI hardware displays and literature about MIDI typically use the range
     * 1 to 128 instead.
     * <p>
     * It is possible that the underlying synthesizer does not support a
     * specific program. In order to verify that a call to {@code programChange}
     * was successful, use {@code getProgram}.
     *
     * @param  program the program number to switch to (0 to 127)
     * @see #programChange(int, int)
     * @see #getProgram()
     */
    void programChange(int program);

    /**
     * Changes the program using bank and program (patch) numbers.
     * <p>
     * It is possible that the underlying synthesizer does not support a
     * specific bank, or program. In order to verify that a call to
     * {@code programChange} was successful, use {@code getProgram} and
     * {@code getController}. Since banks are changed by way of control changes,
     * you can verify the current bank with the following statement:
     * <pre>
     *   int bank = (getController(0) * 128) + getController(32);
     * </pre>
     *
     * @param  bank the bank number to switch to (0 to 16383)
     * @param  program the program (patch) to use in the specified bank
     *         (0 to 127)
     * @see #programChange(int)
     * @see #getProgram()
     */
    void programChange(int bank, int program);

    /**
     * Obtains the current program number for this channel.
     *
     * @return the program number of the currently selected patch
     * @see Patch#getProgram
     * @see Synthesizer#loadInstrument
     * @see #programChange(int)
     */
    int getProgram();

    /**
     * Changes the pitch offset for all notes on this channel. This affects all
     * currently sounding notes as well as subsequent ones. (For pitch bend to
     * cease, the value needs to be reset to the center position.)
     * <p>
     * The MIDI specification stipulates that pitch bend be a 14-bit value,
     * where zero is maximum downward bend, 16383 is maximum upward bend, and
     * 8192 is the center (no pitch bend). The actual amount of pitch change is
     * not specified; it can be changed by a pitch-bend sensitivity setting.
     * However, the General MIDI specification says that the default range
     * should be two semitones up and down from center.
     * <p>
     * It is possible that the underlying synthesizer does not support this MIDI
     * message. In order to verify that {@code setPitchBend} was successful, use
     * {@code getPitchBend}.
     *
     * @param  bend the amount of pitch change, as a nonnegative 14-bit value
     *         (8192 = no bend)
     * @see #getPitchBend
     */
    void setPitchBend(int bend);

    /**
     * Obtains the upward or downward pitch offset for this channel. If the
     * device does not support setting pitch bend, this method always returns
     * 8192. Calling {@code setPitchBend} will have no effect then.
     *
     * @return bend amount, as a nonnegative 14-bit value (8192 = no bend)
     * @see #setPitchBend(int)
     */
    int getPitchBend();

    /**
     * Resets all the implemented controllers to their default values.
     *
     * @see #controlChange(int, int)
     */
    void resetAllControllers();

    /**
     * Turns off all notes that are currently sounding on this channel. The
     * notes might not die away instantaneously; their decay rate is determined
     * by the internals of the {@code Instrument}. If the Hold Pedal controller
     * (see {@link #controlChange(int, int) controlChange}) is down, the effect
     * of this method is deferred until the pedal is released.
     *
     * @see #allSoundOff
     * @see #noteOff(int)
     */
    void allNotesOff();

    /**
     * Immediately turns off all sounding notes on this channel, ignoring the
     * state of the Hold Pedal and the internal decay rate of the current
     * {@code Instrument}.
     *
     * @see #allNotesOff
     */
    void allSoundOff();

    /**
     * Turns local control on or off. The default is for local control to be on.
     * The "on" setting means that if a device is capable of both synthesizing
     * sound and transmitting MIDI messages, it will synthesize sound in
     * response to the note-on and note-off messages that it itself transmits.
     * It will also respond to messages received from other transmitting
     * devices. The "off" setting means that the synthesizer will ignore its own
     * transmitted MIDI messages, but not those received from other devices.
     * <p>
     * It is possible that the underlying synthesizer does not support local
     * control. In order to verify that a call to {@code localControl} was
     * successful, check the return value.
     *
     * @param  on {@code true} to turn local control on, {@code false} to turn
     *         local control off
     * @return the new local-control value, or false if local control is not
     *         supported
     */
    boolean localControl(boolean on);

    /**
     * Turns mono mode on or off. In mono mode, the channel synthesizes only one
     * note at a time. In poly mode (identical to mono mode off), the channel
     * can synthesize multiple notes simultaneously. The default is mono off
     * (poly mode on).
     * <p>
     * "Mono" is short for the word "monophonic," which in this context is
     * opposed to the word "polyphonic" and refers to a single synthesizer voice
     * per MIDI channel. It has nothing to do with how many audio channels there
     * might be (as in "monophonic" versus "stereophonic" recordings).
     * <p>
     * It is possible that the underlying synthesizer does not support mono
     * mode. In order to verify that a call to {@code setMono} was successful,
     * use {@code getMono}.
     *
     * @param  on {@code true} to turn mono mode on, {@code false} to turn it
     *         off (which means turning poly mode on)
     * @see #getMono
     * @see VoiceStatus
     */
    void setMono(boolean on);

    /**
     * Obtains the current mono/poly mode. Synthesizers that do not allow
     * changing mono/poly mode will always return the same value, regardless of
     * calls to {@code setMono}.
     *
     * @return {@code true} if mono mode is on, otherwise {@code false} (meaning
     *         poly mode is on)
     * @see #setMono(boolean)
     */
    boolean getMono();

    /**
     * Turns omni mode on or off. In omni mode, the channel responds to messages
     * sent on all channels. When omni is off, the channel responds only to
     * messages sent on its channel number. The default is omni off.
     * <p>
     * It is possible that the underlying synthesizer does not support omni
     * mode. In order to verify that {@code setOmni} was successful, use
     * {@code getOmni}.
     *
     * @param  on {@code true} to turn omni mode on, {@code false} to turn it
     *         off
     * @see #getOmni
     * @see VoiceStatus
     */
    void setOmni(boolean on);

    /**
     * Obtains the current omni mode. Synthesizers that do not allow changing
     * the omni mode will always return the same value, regardless of calls to
     * {@code setOmni}.
     *
     * @return {@code true} if omni mode is on, otherwise {@code false} (meaning
     *         omni mode is off)
     * @see #setOmni(boolean)
     */
    boolean getOmni();

    /**
     * Sets the mute state for this channel. A value of {@code true} means the
     * channel is to be muted, {@code false} means the channel can sound (if
     * other channels are not soloed).
     * <p>
     * Unlike {@link #allSoundOff()}, this method applies to only a specific
     * channel, not to all channels. Further, it silences not only currently
     * sounding notes, but also subsequently received notes.
     * <p>
     * It is possible that the underlying synthesizer does not support muting
     * channels. In order to verify that a call to {@code setMute} was
     * successful, use {@code getMute}.
     *
     * @param  mute the new mute state
     * @see #getMute
     * @see #setSolo(boolean)
     */
    void setMute(boolean mute);

    /**
     * Obtains the current mute state for this channel. If the underlying
     * synthesizer does not support muting this channel, this method always
     * returns {@code false}.
     *
     * @return {@code true} the channel is muted, or {@code false} if not
     * @see #setMute(boolean)
     */
    boolean getMute();

    /**
     * Sets the solo state for this channel. If {@code solo} is {@code true}
     * only this channel and other soloed channels will sound. If {@code solo}
     * is {@code false} then only other soloed channels will sound, unless no
     * channels are soloed, in which case all unmuted channels will sound.
     * <p>
     * It is possible that the underlying synthesizer does not support solo
     * channels. In order to verify that a call to {@code setSolo} was
     * successful, use {@code getSolo}.
     *
     * @param  soloState new solo state for the channel
     * @see #getSolo()
     */
    void setSolo(boolean soloState);

    /**
     * Obtains the current solo state for this channel. If the underlying
     * synthesizer does not support solo on this channel, this method always
     * returns {@code false}.
     *
     * @return {@code true} the channel is solo, or {@code false} if not
     * @see #setSolo(boolean)
     */
    boolean getSolo();
}