Please let me suggest something abysmal. But maybe useful.
Turn on the musical layout for the alphanumeric keyboard. Four rows of keys set as if they were two octaves in a musical keyboard. W as a C3, S as a C#3, comma (,) and A as a C4 (repeated).
Optionally, you can transpose them (for example, to start from F or G).
Play on the alphanumeric keyboard, and record. Dynamics will be fixed, but note starts and lengths will be exactly as performed.
Cheap, compact, immediate. No need of an external keyboard. (But my company sells excellent inexpensive and compact MIDI keyboards! Buy them in any case!)