Getting Pitch with VB.net

I want to get the pitch of a song at any point. I plan on storing the pitches later. How can I read say... an mp3 file or wav file to get the pitch played at a certain point?

Here is a visual example:

Thanks if you can!

The matter is a tad more complicated than you may be anticipating.

While time-domain approaches exist (that is, approaches which work with the PCM data directly), frequency-domain pitch detection is going to be more accurate. You can read a very simplified overview here.

What you probably want is a Fourier Transform, which can be used to transform blocks of your signal from time-domain to frequency-domain (that is, a distribution of frequency content over a given span of the signal). From there, you would need to analyze the frequency spectrum within that block. The problem becomes even harder still, because there is no best way to deduce pitch from a sampled frequency spectrum in the general case. The aforementioned Wikipedia article should give you a foundation for looking into those algorithms.

Finally, it's worth noting that this is really a language-agnostic question, unless your primary interest is in reading a WAV file specifically using VB.NET.