How to make real-time frequency detector

Hi, I could make frequency detector(actually frequency analyzer) when I input several second with laptop microphone.

And, what i wanna make is real-time frequency detector. I made it with Processing (check out processing.org) with simple code.

The code i made is like below.

time_rec = 15;
fs = 8000;

recObj = audiorecorder(fs,16,1);
set(recObj,'TimerPeriod',0.1,'TimerFcn',@call); 
record(recObj,time_rec);

sound(x);

function [x] = call(h,~)
  x = getaudiodata(h);
  X = fft(x);
  N = length(X);
  P = abs(X/N);
  Amp = P(1:N/2+1);
  Amp(2:end-1) = 2*Amp(2:end-1);
  fs = 8000;

    f = fs*(0:(N/2))/N;
    hold off;
    plot(f, Amp);
end

And it acts like cumulative analyzer, which have memory. What should i fix to make it real-time?