>But the OP-1 is literally the only piece of music gear you can bring on an airplane and write a whole song. Show me another way to write a song in an airplane,

>But the OP-1 is literally the only piece of music gear you can bring on an airplane and write a whole song. Show me another way to write a song in an airplane, and you can have my money. Assuming you mean without using a phone, computer, or a tablet: Yamaha Reface DX ($400) + Korg SOS Recorder ($100) + TE PO-12 Rhythm ($60), and you not only have a portable studio, but a performer's rig. I'm powering mine from a powerbank via a USB-to-12V adapter, it lasts forever on a charge. I can busk with Reface DX alone (it's built-in speakers are loud enough for a quiet street). Throw in a mini-amp, and it's a band. And it comes with an optional keytar strap too, so I cann sling it around my shoulder. And it's the best FM synthesizer ever made. Worth it for the E-Piano patch and Final Countdown-like leads alone, but the real magic comes in realtime manipulation of sound (something you couldn't do with the clunky controls of DX-7). Yeah, I don't know if it fits your "all-in-one" defitinion, but surely OP-1 doesn't fit mine: it's missing a proper keyboard (my main rig is Yamaha MX-88, and I still say that Reface DX's keyboard is great). And with some creative application of electrical tape, the drum machine / field recorder just become upgrades for the Reface DX, giving yout the ultimate unit.