delphi - 如何在Delphi中改变MIDI音符的音高和音量？

Question

我在项目中使用以下代码在按键时播放 midi 音符(这是源代码中与 midi 相关的部分):

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;

我知道有 MIDI 消息可以改变音高和音量。但我在delphi中找不到任何使用它们的例子。请帮助我修改 playNote 程序，使声音类似于吉他弯音效果(半音或全音调上演奏的音符的平滑音调变化)，并类似地改变音符的音量(淡入)和淡出效果)。

提前谢谢您!

Answer 1

我找到了解决方案。

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;

删除TProgressBar在表单上，​​并设置其 Min和Max至0和16383 ，分别。

然后您可以通过滚动鼠标滚轮来“弯曲”音调。 (请注意，我在处理鼠标滚轮时使用的因子 4 可能不适合您的鼠标和当前的鼠标设置。)

示例:pitchbend.exe [我从我的网站中删除了该 EXE 文件，因为 Google Chrome 认为它是恶意软件。尽管这几乎肯定是误报，但我担心这会对我的 Google 排名产生负面影响。]