Not clear what exactly do you mean by "Note Analysis". It can range from tone recogntion by raw audio input (very difficult matter, related to both Fourier analysis and image recognition, especially difficult of both tones and durations should be recognized in polyphonic input; I simply don't know any existing products of reasonable quality) to some calculations in music theory which do not require any media capabilities at all.
As to MIDI libraries (why DLL? a VB.NET unit, library or not, is always assembly; in .NET the notion of .DLL is nothing but a file name pattern, and it can be anything), there are several good libraries published on CodeProject:
http://www.codeproject.com/search.aspx?q=MIDI&doctypeid=1[
^].
I was quite satisfied with at least one of them. Sorry, I don't remember which one exactly — try them by yourself.
—SA