Question

I use the following code in my project to play midi note on key press (this is midi-related part of source):

uses
MMSystem;

var
hMidi, midimsg, notenum, instrumNum :integer;

procedure TForm1.FormCreate(Sender: TObject);
begin
  midiOutOpen(@hmidi, 0, 0, 0, 0);
  midimsg := $C0+$100*29; // set midi instrument to overdriven guitar (29th in GM midi instrument list)
  midiOutShortMsg (hmidi, midimsg);
end;

procedure playNote(var note:integer);
begin
  midimsg := $90 + (note * $100) + (127 * $10000) + 0;
  midiOutShortMsg (hmidi, midimsg);
end;

procedure stopNote(var note:integer);
begin
  midimsg := $80 + (note * $100) + 0 ;
  midiOutShortMsg (hmidi, midimsg);
end;

procedure TForm1.FormKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
  playNote(60);
end;

procedure TForm1.FormKeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
  stopNote(60);
end;

procedure TForm1.FormClose(Sender: TObject; var CloseAction: TCloseAction);
begin
  midiOutClose(hmidi);
end;

I know that there are midi messages to change the pitch and volume. But I could not find any examples of their usage in delphi.
Please, help me to modify the playNote procedure to make sound similar to guitar bend effect (smooth pitch shift of played note on semitone or whole tone up) and similarly to change the volume of note (fade-in and fade-out effect).

Thank you in advance!

Answer 1

I found a solution.

const
  MIDI_NOTE_ON = $90;
  MIDI_NOTE_OFF = $80;
  MIDI_CHANGE_INSTRUMENT = $C0;
  MIDI_PITCH_BEND = $E0;

function MIDIEncodeMessage(Msg, Param1, Param2: byte): integer;
begin
  result := Msg + (Param1 shl 8) + (Param2 shl 16);
end;

procedure TForm4.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  midiOutClose(hMidi);
end;

procedure TForm4.FormCreate(Sender: TObject);
begin
  playing := false;
  midiOutOpen(@hMidi, 0, 0, 0, CALLBACK_NULL);
  midiOutShortMsg(hMidi, MIDIEncodeMessage(MIDI_CHANGE_INSTRUMENT, 19, 0));
end;

procedure TForm4.FormKeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
  if playing then Exit;
  ProgressBar1.Position := $2000;
  midiOutShortMsg(hMidi, MIDIEncodeMessage(MIDI_PITCH_BEND,
    lo(ProgressBar1.Position), hi(ProgressBar1.Position)));
  midiOutShortMsg(hMidi, MIDIEncodeMessage(MIDI_NOTE_ON, 50, 127));
  playing := true;
end;

procedure TForm4.FormKeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
  midiOutShortMsg(hMidi, MIDIEncodeMessage(MIDI_NOTE_OFF, 50, 127));
  playing := false;
end;

procedure TForm4.FormMouseWheel(Sender: TObject; Shift: TShiftState;
  WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
begin
  ProgressBar1.StepBy(4*WheelDelta);
  midiOutShortMsg(hMidi, MIDIEncodeMessage(MIDI_PITCH_BEND,
    lo(ProgressBar1.Position), hi(ProgressBar1.Position)));
end;

Drop a TProgressBar on the form, and set its Min and Max to 0 and 16383, respectively.

Then you can ‘bend’ the pitch by scrolling your mouse wheel. (Notice that the factor 4 I use when handling the mouse wheel might be unsuitable for your mouse and your current mouse settings.)

Sample: pitchbend.exe [I removed the EXE file from my website because Google Chrome considered it to be a malware. Although this was almost certainly a false positive, I was afraid that it would have a negative effect on my Google rankings.]