Diatonic is just what you need for intelligent harmonies, but it is monophonic. Pitchflex is great for mimicking the whammy pedal, or transposing a guitar tuned to 440 down to Eb or any amount down to two octaves down. Octaver is just that. H910/H949 is good for that 80s pitch define sound Eddie used on songs like Panama. Synthonizer is monophonic, and I haven’t had much luck with it. It tends to sound jittery and quite unmusical. I haven’t put a lot of time into it, so it’s probably just user error. Not sure about any other