DFT (Discrete) and FFT Fast Fourier Transform Matlab Examples

I need Matlab examples on FFT. The examples must be made as clearly as possible. By this I mean it has to be a step-by-step, with all of the steps explained and thorougly commented, to lead to the final answer. The examples should be based on a known frequency .wav files; like, for example, a 440Hz wav file, or a DTMF file (there should be a DTMF file. These .wav files should be made also using Matlab. Then, these .wav files would be "processed" by this Matlab example. By processed, I mean, but not only: to plot the original file; get the samples (and here well commented on what happens if you get more samples, the influence of amount of samples on lower frequencies and higher frequencies, etc), do the FFT, plot, reconstruct the frequency based on the FFT, plot. All of the steps must have, and I insist on the must, a very well commented explanation on what is happening. The objective here of this project is to have plentiful of examples and to understand DFT and FFT. If freelancer wishes, and I do prefer, I can check all the steps and keep this communication open to check the progress and keep freelancer aware of what is being done and I can also raise questions. *****No initial milestone will be granted. I will place the full milestone before project starts, but it will only be released, if, and only if, the project meets what I need. ****No Matlab toolbox should be used!!!