Yes you can. The vocal harmonizers are getting away from using midi though. T.C. Helicon Perform VK still uses it, but also has the option to follow the music by audio input, and even by a built-in mic.
I'm still using the aging T.C. Helicon Harmony M, because it does everything I need. I tried a VK and although it had many wonderful new features, I didn't use them, so went back to the Harmony M. In fact I have two of them, as I like to have a backup for everything, and they are hard to find these days, since they haven't been made in several years.
But to answer your question, it reads the chord information so will work just fine with simple one-note chords. However if you want to use the Vocoder mode, you'll have to play the notes.
Hope this helps.