I admit I haven't tackled the manual yet so maybe there's some kind of setting with which I can fiddle with its pitch detection?  Here's my problem: If I play two notes on my guitar an octave apart and then use Melodyne Editor's polyphonic algorithm to convert them to MIDI, all I get is one note. In fact I'm finding that the polyphonic pitch detection doesn't work quite as well as I thought it would. I also tried playing a repeating bass note with my thumb and picking out a melody above it. It caught the bass notes well enough, but omitted quite a few of the melody notes. This is a very clean recording of a guitar (DI) and yes I'm articulating the notes very cleanly.  The other day I also found that when playing 5 or 6 note chords with a pick, Melodyne would often fail to detect the top note of the chord even though it rang out as clear as a bell in the recording. Does anyone have any tips for making this polyphonic pitch detection work better?

Did you try the detection mode? I suspect there will be a "transparent"-like blob an octave higher which Melodyne "discarded"...You can then indicate that it's actually a note. Once done, you can go back to the normal mode and there it will show up. Check this tutorial:
 
http://helpcenter.celemony.com/editor2/en/singletrack_tour_31.html
 
 
 

I have the same issue in melody mode. I think it may have issues with overdriven guitar being the source material, going to experiment over the weekend.

3dmus
Did you try the detection mode? I suspect there will be a "transparent"-like blob an octave higher which Melodyne "discarded"...You can then indicate that it's actually a note. Once done, you can go back to the normal mode and there it will show up. Check this tutorial: http://helpcenter.celemony.com/editor2/en/singletrack_tour_31.html   

All that appeared when I created the Melodyne clip was a single note, there were no other blobs.

That's because you need to enter "detection mode".  Check out the manual or the videos.  Once you get the hang of it, it's amazing.
 
Detection mode also shows other potential notes, and you can choose the correct ones.

js516
I have the same issue in melody mode. I think it may have issues with overdriven guitar being the source material, going to experiment over the weekend.

Overdriven sounds are particularly unsuitable for detection, because the overdrive creates a lot of harmonic content. If you have the option, record clean and apply fx later, or run a dual input, one clean and one overdriven.

jb101
That's because you need to enter "detection mode".  Check out the manual or the videos.  Once you get the hang of it, it's amazing.
 
Detection mode also shows other potential notes, and you can choose the correct ones.

 
That doesn't do it. As an example, try playing two A notes an octave apart on a guitar. Melodyne will only detect the lower note and won't recognize the higher one at all. I tried detection mode - it doesn't give any other "possible" notes. I have just read an online review of Melodyne elsewhere where it talked about how Melodyne will frequently fail to recognize octaves, so I'm thinking it's just a limitation of the software. 

Hmm so I tried this again but with two notes considerably higher up the neck, and the top octave notes were given as potentials this time. Back to the drawing board!

With the lower octaves, did you try moving the Crescent of the Note Assignment Slider in Note Assignment mode?  This can increase the number of Potential Notes.
 
Did you try sliding it fully to the left and moving mouse around to find Energy Images (ghosted images that are Undetected(sic) notes that can be activated as Potential or Active Notes)?

Octaves are probably the most difficult to detect, since so many overtones overlap.