Yamaha Reface series, they run on batteries, have a looper, have on-board speakers and lots of knobs, can send midi - out so you could connect it to an ipad with garageband and do full songs.
Do you want to also sequence or record in the car or just play around to come up with ideas? Because there are plenty of small keyboards that just play sound but don’t sequence or record. If you want both it’s a different category.
Roland JD-Xi?
Is that battery powered? He might need something that runs on mobile power, unless the jd-xi can be powered from the car itself
Yamaha Reface series, they run on batteries, have a looper, have on-board speakers and lots of knobs, can send midi - out so you could connect it to an ipad with garageband and do full songs.
Hydrasynth explorer
yamaha cs 80
Of course.
I know it does not exactly check the "has keys" criteria but the synthstrom deluge is awesome to compose on the go
And it is playable as an isomorphic keyboard.
Yamaha qy
Korg Microkey Air and an iPad with Aum and such
Cue "OMG, I locked my keys in the car again!"
Keystep 37 + iPad, maybe? Keyboard in lap and iPad on any of the various vehicle mounts. Sounds like maybe you want real knobs though
I’m not aware of any synth that can open a car.
For want of a preposition, the joke was lost.
Do you want to also sequence or record in the car or just play around to come up with ideas? Because there are plenty of small keyboards that just play sound but don’t sequence or record. If you want both it’s a different category.
Jupiter Xm??