I’m torn between getting the A4 or the Keys.
Something that I really want to do is work on tracks on the couch while watching movies and whatnot. Is that possible with the Keys, to use it on your lap?
That use case really lends itself to the A4, but I love the enhanced functionality of the Keys. Maybe I can actually build up some keyboard chops with it too?!
In addition to the ‘mobility’ question, any insight to help me decide between these two would be awesome.
Sometimes i bring my Monomachine with me, just to try to get sleep fast like reading a book.
But the result is the opposite, i create something nice and at the end, i sleep less than i wanted.
I choose monomachine because it’s digital and will not suffer about overheat, especially in summer.
The A4 is warmer and need some good ventilation, i don’t advice to use on laps, at least on summer.
Maybe you can use one of them: http://www.ikea.com/us/en/catalog/products/10278243/
About anlaog keys, well, i don’t have one, but from the size, i wouldn’t bring it with me on bed. I still prefer my girlfriend.
After using an A4 for months, and longing for a Keys, I came to the solution of A4 + Novation Xiosynth 25.
I get joystick for pitch + mod. an XY pad, additional assignable knobs for midi CC (so I can use Performance mode while also tweaking some track filters and such). The main thing I am lacking with this combo is aftertouch, but I can assign things to the XY pad to somewhat make up for that.
Also, the Xiosynth gives me a 3 OSC virtual analog synth that I can send the audio output of into the A4, as an OSC. They hybrid mode allows the two to work nicely together.
Battery powered, and more portable than AK. Worth consideration.
I have the Keys and recently added the Rytm.
You can use the Keys on the couch, but it’s hardly the most ergonomic solution. If you put it in your lap, even with a lap-desk, you have to do “Tyrannosaurus Rex arms” to play the keys and then your elbows are poking into the couch cushions.
If you put it on a tray table or a typical keyboard stand, it ends up too high because you are sunk into the couch cushions.
I’ve had the best results putting it on an ottoman that puts it at the right height for my hands and sitting on the edge of the couch, but even then I have to kind of lean over to counteract the natural tendency of the couch to suck you into a lazy slouch.
Simply not the best experience.
The Rytm, on the other hand, is totally a use-anywhere device (as long as you have somewhere to plug it in and headphones). On the couch, in bed, on a train/plane that has outlets…it’s very happy to travel. And chromatic mode means I can easily write a whole song on the Rytm, so I don’t mind leaving the Keys behind when I do go Elektronomadic.
I do love the Keys, and the features it adds. And Overbridge is not going to diminish that opinion, because individual outputs that require a computer-sized dongle to work are not the same as built-in 1/4-inch outputs. 
If you think those features are worth having, I’d advise you to get it and just use something else on the couch - the XioSynth is pretty cheap, as are apps for the iPad if you already have an iPad, or one of the Pocket Operators, or an old Yamaha QY-70, or a Volca.
If you think you can live without the AK’s extras, then get the A4 and join the Elektronomad caravan.
Thanks people. Very helpful, particularly your comments Mies van der Robot. That really steers me toward the A4.
The idea of comfortable couch use is great. And so is taking it out and about with a portable battery.
The keys seem to add a richness to the experience, but I believe I’m prioritizing convenience. I can upgrade if that makes sense after some use with the A4.
Now I just need to commit for A4 over Rytm first. I definitely want both but first…think it’s going to be the A4. The sound is more captivating to me. Ah, choices.
I’m coming form at OT by the way…a couple years ago. Well I have one again, but it is defective - still sorting that out.
I have a A4 and a AK. I make music in a small caravan 5.50 m by 2.30 m.
I started withe tha A4 and this one is easy to use inon your lap but it gets WARM ! I take both into bed sometimes. But on my lap the AK is to big
What I like alot is to have my AK on my desk with the A4 on my lap - both instruments can control veverything from eatch-other witch is just GREAT !
What I like about the AK is the weight - it’s not heavy - and 3 octaves is perfect for me.