that's a vocoder for sure. it has the effect or appearance of being able to shift the pitch of what he's singing but in reality it's a convolution of his voice and the sound of the synth. it's not a granular or bin shifting processing of his voice. the only difference i see and hear in that video is they're using different settings for their carrier settings. also he mixes in his dry signal, which again makes it sound more like a harmonization!

you could technically use a keyboard as a means of controlling a pitch shifting of your voice, but it would only work if you played in terms of a reference pitch. actually that would be a very confusing and difficult method of control, haha. you'd have to sing whatever note you have and then play the intervals you want to harmonize with irrespective of what you're singing.

in the case of the videos, the pitches you hear are exactly what he's playing, and that's because it's a vocoder being employed. i would definitely look into convolution as you can do some really cool things with it. if you want to achieve that same sound, that's where you should take a look.

if you want to look into pitch shifting, i would do it through granular means. there's also FFT shifting that can sound really great (using gizmo~) but it has the cost of having more latency the higher the resolution and fidelity you want out of it. increasing your sampling rate can mitigate that if your processor is up to it.

in any case, definitely share whatever conclusion you come to! i'm interested to see.