GaryExo,
I use a very simple MIDI keyboard. My current model is M-Audio's KeyStudio, which is small enough to fit on my office desk. It has no internal sounds — it is simply a piano-style, USB entry keyboard with four octaves, a pitch bender, a mod wheel, and another couple of buttons. It also has a jack for a sustain pedal, but that is still irrelevant for Notion work.

As I recall, it cost me about $80. For anything resembling the authentic feel of a piano, it fails as a miserable piece of junk, but as an input device it serves me just fine about 99% of the time.
Best wishes,
Thorrild
Oh, I forgot: This keyboard is also sufficient to test NTempo control of a score before I release it into the real world for "live" performance.