KORG microKEY Air 37
Well, this one is certainly more portable than the Novus.
The kids can't get enough of it, it's just so fun and versatile. There are a ton of sounds and music tools on iOS with the KORG software. For example, the Marseille gadget has a highly customizable Toy Piano tone which rivals the Reface dedicated one in every way, but although that tone is fun, admittedly, the novelty wears off fairly quickly.
Bluetooth MIDI + Background Audio on iOS is key. I already had KORG Module, GarageBand with the extra instrument packs, and this pushed me over the fence to get the new KORG Gadget 2 which also integrates the Module sounds. It can drive all my MIDI apps simultaneously but that's probably just an iOS feature. KORG is like the Nintendo of the music world.
The pitchbend wheel feels really good and the octave buttons are nicely implemented with the LEDs. It obviously lacks all the physical controls that the Reface sports, but on the other hand, I don't actually need a knob with a dedicated Toy Piano setting.
37 keys seems to be the right choice for portability. It'll fit in my main luggage for travel. On the other hand, it's only just a backup -- my Novus and Privia Slim aren't going anywhere.
The key action takes some getting used to. It's a bit spongy and a bit noisy, but by the end of the day, I was used to it. I needed to adjust the velocity curve, and even so, this doesn't come anywhere near to matching the control and expressivity on the Novus.
I can certainly practice key fingerings on this, but expression/dynamics-wise, I'm not so sure. This is also probably down to muscle memory, but I can't recover from mistakes and resume as easily as I can on the Novus once I miss a note.
Configuring the velocity curve can be done temporarily in KORG Module or permanently using the KORG Kontrol Editor which can also configure a few other things. Unfortunately, Kontrol is abandonware that only runs on PC/Mac. It is super painful to use on PC/Mac but that is the only way to permanently write settings to the keyboard -- and forget doing it over Bluetooth MIDI. At one point, after using Kontrol, I thought I had bricked my keyboard, but I just needed to manually unpair and repair it.
The keys are cut like piano keys, which is a nice touch and feel better than "overhanging" style keys. The key sizes, however, take some getting used to. The white keys are fine, but the black keys need some patience, especially with octave chords that go on the black keys. I can make it work, but still, it's a stumbling block.
White keys are 80mm x 19mm and black keys are 42mm x 8mm. I'm curious as to how they compare to the Reface, because if the Reface has longer keys, then it would have potentially been a better buy for me. The length of the black keys is my single biggest reservation, and this is despite the fact that my hands are quite presidential, size-wise.
I take this keyboard with me literally everywhere. I'm considering taking it to work and hooking it up with MIDI to keystroke software for keyboard shortcuts.
Ref. Piano World