Arising out of a conversation in https://www.steinberg.net/forums/viewtopic.php?f=246&t=181612, I bought an Akai LPK25 MIDI keyboard for note input. It is about 335 mm wide and comes with a cable that plugs into a USB-A socket on the computer. I plugged it straight in and turned it on (USB-powered). There is a light that flashes continually, called tap tempo. Reading the quickstart guide, I discover that the switch to the left of it turns this light off.
The biggest drawback is not the fact that it only has a span of 2 octaves, but that the keys are very narrow. Most pianos have an octave width of about 165 mm, my large harpsichord is 158 mm, whereas the Akai octave is only 137 mm. In combination with the heavy spring-loaded keys, this means that there is little likelihood of my being able to play this keyboard accurately while looking at the Dorico display. Normal transposition of the keyboard places middle C in the centre, but this can be transposed by +/-4 octaves, which is more than adequate for anything I write. I have managed to produce 11-note chords without difficulty. The keyboard works without the Dorico window needing to be selected. I have not yet investigated whether the top four notes, which are labelled Pro1, 2, 3 & 4 respectively, can be used to trigger Dorico commands – another day, perhaps…
I wasnt expecting a concert instrument for €45, and it remains to be seen whether I can become any kind of virtuoso on the Akai LPK25; but if using it proves faster than typing note names it will be of of great help.