Alright, so I have searched everywhere to try to find this out. I've looked at source code for spectrograms, various online tutorials. But they all miss what I am looking for. And for some of them, even if I copied their code word for word half the methods/classes they used didn't exist. Which means they left out some of the libraries they used, or other classes they made, making their tutorial/code rather useless to me, as I have no way to find out what they used.
So to sum it up. I am new to FFT, and other sound related manipulations. I need to learn how to acquire a sound source. I am trying to find out how I can even get the frequency, and the amplitude of that frequency, from a sound source. After that, all I need to do is to feed the acquired data into a painter, and then display the result. As well as making the GUI, which there should be plenty of tutorials to choose from.
Note: I am open to using other programming languages.