Multimedia Tools, TMMPeakDetect & FFTLength

Multimedia Tools, TMMPeakDetect & FFTLength

I am working with Multimedia Tools and TMMPeakDetect component.
And I have one question.

What is FFTLength (Fast Fourier Transform) ?

When I set FFTLength to 64 and after that to maximal 16384, the details of sound frequency volume are different.

I need true details about sound.

Is that have some things with sound quality (if we put FFTLength higher or lower and get sound frequency amplitude) ?

It is maximal true if I put FFTLength to 16384 ?

In how many decimals goes frequency in computers ?

This is a code :

procedure TForm1.Button1Click(Sender: TObject);
var frequency:integer;
begin
frequency:=0;
Memo1.Clear;
while frequency<1500 do
begin
memo1.Lines.Add(inttostr(frequency)+'_'+inttostr(MMPeakDetect1.GetPeakIndex(frequency))+'_'+inttostr(MMPeakDetect1.Peaks[MMPeakDetect1.GetPeakIndex(frequency)]));
inc(frequency)
end;
end;

The problem is that I want to set with this informations (TMMPeakDetect) about 41000 TMMGenerators and simulate sound of music in real-time.

Thanks.