Appreciate helping me with this lab assignment.

[Mohammad Sami]

You need to answer the questions, then if you run into specific problems, you can show your code and ask about the problem you are facing.

[Amr Ashraf Hafiz]

im facing a problem in steps from 16 to 19

[Amr Ashraf Hafiz]

This is the code i have written .

% the musical notes are sinusoidal waves
fo=440; %fo=440HZ
fdo=440*(2^(-9/12));%the frequency of musical note "DO" for n=-9
%C-major musical scale [DO,RE,MI,FA,SOL,LA,TI,DO]
ncmajor=[-9,-7,-5,-4,-2,0,2,3];
fn=fo*2.^(ncmajor/12);% frequencies of musical notes
%the difference between the integers "n" correspond to the musical notes
nmajor=diff(ncmajor);
n=[0,nmajor];
ncmajor=cumsum(n);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
n=[-9,-7,-5,-4,-2,0,2];
fn=fo*2.^(n/12);
f15=fo*2.^(15/12);
f=[fn,2*fn,f15];
time=500;%half a second(0:500msec)
t=0:time-1;
wrectT=rectwin(time);
x15=wrectT'.*cos(2*pi*f15*t);
plot(t,x15)% for DO note at f15
for t = 0:time-1
 xn=wrectT*cos(2*pi*f*t);
end

[Walter Roberson]

What is your question?

http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

[Amr Ashraf Hafiz]

I couldn't compose a 20 secs audio piece of music as it is asked to do in step 19

[Walter Roberson]

for t = 0:time-1
 xn=wrectT*cos(2*pi*f*t);
end

Every iteration of that loop, you overwrite all of xn .

for t = 0:time-1
 xn(t+1) = wrectT*cos(2*pi*f*t);
end

Your code also needs to take into account sampling frequency. You need to sample at least twice as fast as your highest frequency note.

time=500;%half a second(0:500msec)

That implies you are thinking in terms of sampling once per millisecond, However, millisecond is only 1000 Hz and your last major cord is at 523.251130601197 Hz, so your sampling frequency needs to be above 1047 Hz.