The question of converting an analogue sound to a midi output has been going round since just after midi was invented. Plenty of different manufacturers and plain ordinary experimenters have had moderate to good success with just one instrument at a time, but throw in more instruments and then things get confusing as to what will come out.
However Sibelius and Finale incorporated mic to notation a good few years ago, though how good that was depended on both the microphone used and the instrument in question.
The real problem isn't just one note, when with good hearing for pitch, you can say that is middle C or a even an F sharp, most analogue to midi systems can manage that, it is when it comes down to you or I can say it is a piano playing the C and a trumpet playing the F sharp is where systems fall apart and that is because we can identify the harmonic content of those notes, which gives us the means to identify what played them, and for different instruments there are many harmonics in some, I dread to think of a full display of one note from a sax for example.
So add all that lot to the human voice which is different for each person, I reckon that any conversion from A to M is going to be a struggle for either software or hardware to match successfully with every note sung, and even more so if another instrument is being played along side it.