piano synthesis

Hello,

I am doing a project that asks the user for a note number and producing a piano sound with that pitch. I am trying to achieve this through additive synthesis (if there are simpler ways, let me know) and right now I have made a sound much like that of a kazoo with a fundamental plus 24 partials. Here is some of the code:

srate = 44100;

ff = 27.5*2^((noteNumber-1)/12);

t = (0:1/srate:2);

mag = [1, .7, .95, .75, .6, .65, .65, .5, .6, .5, .45, .5, .6, .5, .25, .5, ... 
    .3, .25, .3, .4 , .4, .3, .25, .2, .15]; 

for i = 1:25
    y = y + mag(i)*sin(2*pi*ff*i*t);
end

*Note: The numbers in mag represent the amplitude coefficients which were selected somewhat arbitrarily and through analysis of a piano sound.

Ideally, I want to create something like one of these two samples.

http://www.acoustics.salford.ac.uk/student_area/bsc3/acoustics_music/electronic_music/sample%20sounds/Piano.Wav

http://www.acoustics.salford.ac.uk/student_area/bsc3/acoustics_music/electronic_music/sample%20sounds/PVpianoafter.wav

How would I achieve these? I know I need to add the percussive hammer sound in the beginning and some inharmoncities. How can I make a sound like the ones shown above? Some help/code would be greatly appreciated. Thank you