>> the OP-1 is literally the only piece of music gear you can bring on an airplane and write a whole song.
Apart from...
* Laptop with your favourite DAW
* iPad with GarageBand or Android Tablet with Caustic
* I would put Novation Circuit in similar category though depends on your definition of whole song
* Synthstorm Deluge
* Digitakt Elektron?
* Some of the Roland grooveboxes and systems
* Some of the Akai APC/MPC or Native Instruments Machine? Not fully familiar with either but I thought e.g. Akai Live lets you do a full production
* Bunch of other stuff I'm sure I'm forgetting
I feel we are actually in a bonanza and cornucopia of portable music creation devices! And that's a good thing :). Heck even the Yamaha Reface is super portable, battery powered, real keyboard, lots of sounds, and you can hook it up to phone or a simple recorder/looper to make good stuff on the go. OP1 might be the smallest by some metrics, that may or may not be seen as a good thing.
Let's add the Nintendo Switch. I can get the KORG Gadget for 30£ and make some sweet tunes. Sure, to get the tunes out into something I can export sound from I'd need to get the KORG Gadget for iOS or Android, and from there to Ableton Live. But I've tried out the KORG Gadget on Switch and it's really fun to use.
Apart from...
* Laptop with your favourite DAW
* iPad with GarageBand or Android Tablet with Caustic
* I would put Novation Circuit in similar category though depends on your definition of whole song
* Synthstorm Deluge
* Digitakt Elektron?
* Some of the Roland grooveboxes and systems
* Some of the Akai APC/MPC or Native Instruments Machine? Not fully familiar with either but I thought e.g. Akai Live lets you do a full production
* Bunch of other stuff I'm sure I'm forgetting
I feel we are actually in a bonanza and cornucopia of portable music creation devices! And that's a good thing :). Heck even the Yamaha Reface is super portable, battery powered, real keyboard, lots of sounds, and you can hook it up to phone or a simple recorder/looper to make good stuff on the go. OP1 might be the smallest by some metrics, that may or may not be seen as a good thing.