matlab - How to get the 10-5 most dominant frequency in an audio signal

I have this wav file that I recorded using my laptop, It contains the sound of a G chord of a guitar. Since the guitar have 6 strings the sound should contain different frequencies I want to determine the top 10 most dominant frequency in the signal.

[X, Fs] = wavread('chordG.wav');
freq = fft(X);
plot(abs(freq)):

I don't know how to proceed after that it shows the graph of the frequency but I don't know how can I extract the values in the graph.

Your answer would be very much appreciated :)