Как разрезать wav файл?

type
  TWaveHeader = record
    ident1: array[0..3] of Char;       // Must be "RIFF"
    len: DWORD;                        // remaining length after this header
    ident2: array[0..3] of Char;       // Must be "WAVE"
    ident3: array[0..3] of Char;       // Must be "fmt "
    reserv: DWORD;                     // Reserved Size
    wFormatTag: Word;                  // format type
    nChannels: Word;                   // number of channels (i.e. mono, stereo, etc.)
    nSamplesPerSec: DWORD;             //sample rate
    nAvgBytesPerSec: DWORD;            //for buffer estimation
    nBlockAlign: Word;                 //block size of data
    wBitsPerSample: Word;              //number of bits per sample of mono data
    cbSize: Word;                      //the count in bytes of the size of
    ident4: array[0..3] of Char;       //Must be "data"
end;
 

You can load the file header with this function:

function GetWaveHeader(FileName: TFilename): TWaveHeader;
const
  riff = 'RIFF';
  wave = 'WAVE';
var
  f: TFileStream;
  w: TWaveHeader;
begin
  if not FileExists(Filename) then
    exit;
 
  try
    f := TFileStream.create(Filename, fmOpenRead);
    f.Read(w, Sizeof(w));
 
    if w.ident1 <> riff then
    begin
      Showmessage('This is not a RIFF File');
      exit;
    end;
 
    if w.ident2 <> wave then
    begin
      Showmessage('This is not a valid wave file');
      exit;
    end;
 
  finally
    f.free;
  end;
 
  Result := w;
end;

Now we have all for creating the code for spliting the wave file:

 
function SplitWave(Source, Dest1, Dest2: TFileName; Pos: Integer): Boolean;
var
  f1, f2, f3: TfileStream;
  w: TWaveHeader;
  p: Integer;
begin
  Result:=False
 
  if not FileExists(Source) then
    exit;
 
  try
    w := GetWaveHeader(Source);
 
    p := Pos - Sizeof(TWaveHeader);
 
    f1 := TFileStream.create(Source, fmOpenRead);
    f2 := TFileStream.create(Dest1, fmCreate);
    f3 := TFileStream.create(Dest2, fmCreate);
 
    {++++++++++Create file 1 ++++++++++++++++}
    w.len := p;
    f2.Write(w, Sizeof(w));
    f1.position := Sizeof(w);
    f2.CopyFrom(f1, p);
    {++++++++++++++++++++++++++++++++++++++++}
 
    {+++++++++++Create file 2 +++++++++++++++}
    w.len := f1.size - Pos;
    f3.write(w, Sizeof(w));
    f1.position := Pos;
    f3.CopyFrom(f1, f1.size - pos);
    {++++++++++++++++++++++++++++++++++++++++}
  finally
    f1.free;
    f2.free;
    f3.free;
  end;
 
  Result:=True;
end;

Взято с Delphi Knowledge Base: https://www.baltsoft.com/