Expressive E Osmose review: A game-changing MPE keyboard, but a frustrating synthesizer

When I first got to see the Expressive E Osmose way back in 2019, I knew it was special. In my 15-plus years covering technology, it was one of the only devices I’ve experienced that actually had the potential to be truly “game changing.” And I’m not being hyperbolic.

But, that was four years ago, almost to the day. A lot has changed in that time. MPE (MIDI Polyphonic Expression) has gone from futuristic curiosity to being embraced by big names like Ableton and Arturia. New players have entered and exited the scene. More importantly, the Osmose is no longer a promising prototype, but an actual commercial product. The questions, then, are obvious: Does the Osmose live up to its potential? And, does it seem as revolutionary today as it did all those years ago? The answers, however, are less clear.

Expressive E Osmose keybed sideview.
Terrence O'Brien / Engadget

What sets the Osmose ($1,799) apart from every other MIDI controller and synthesizer (MPE or otherwise) is its keybed. At first glance, it looks like almost any other keyboard, albeit a really nice one. The body is mostly plastic, but it feels solid and the top plate is made of metal. (Shoutout to Expressive E, by the way, for building the OSMOSE out of 66 percent recycled materials and for making the whole thing user repairable — no glue or speciality screws to be found.)

The keys themselves have this lovely, almost matte finish and a healthy amount of heft. It’s a nice change of pace from the shiny, springy keys on even some higher-end MIDI controllers. But the moment you press down on a key you’ll see what sets it apart — the keys move side to side. And this is not because it’s cheaply assembled and there’s a ton of wiggle. This is a purposeful design. You can bend notes (or control other parameters) by actually bending the keys, much like you would on a stringed instrument.

This is huge for someone like me who is primarily a guitar player. Bending strings and wiggling my fingers back and forth to add vibrato comes naturally. And, as I mentioned in my review of Roli’s Seaboard Rise 2, I find myself doing this even on keyboards where I know it will have no effect. It’s a reflex.

It’s a very simple thing to explain, but very difficult to encapsulate its effect on your playing. It’s all of the same things that make playing the Seaboard special: the slight pitch instability from the unintentional micro movements of your fingers, the ability to bend individual notes for shifting harmonies and the polyphonic aftertouch that allows you to alter things like filter cutoff on a per-note basis.

These tiny changes in tuning and expression add an almost ineffable fluidity to your playing. In particular, for sounds based on acoustic instruments like flutes and strings, it adds an organic element missing from almost every other synthesizer. There is a bit of a learning curve, but I got the hang of it after just a few days.

Expressive E Osmose pitch bend settings.

What separates it from the Roli, though, is its formfactor. While the Seaboard is keyboard-esque, it’s still a giant squishy slab of silicone. It might not appeal to someone who grew up taking piano lessons every week. The Osmose, on the other hand, is a traditional keyboard, with full-sized keys and a very satisfying action. It’s probably the most familiar and approachable implementation of MPE out there.

If you are a pianist, or an accomplished keyboard player, this is probably the MPE controller you’ve been waiting for. And it’s hands-down one of the best on the market.

Where things get a little dicier is when looking at the Osmose as a standalone synthesizer. But let’s start where it goes right: the interface. The screen to the left of the keyboard is decently sized (around 4 inches) and easy to read at any angle. There are even some cute graphics for parameters such as timbre (a log), release (a yo-yo) and drive (a steering wheel).

Expressive E Osmose interface with cute icons for parameters like cutoff, filter resonance and envelope.
Terrence O'Brien / Engadget

There aren’t a ton of hands-on controls, but menu diving is kept to a minimum with some smart organization. The four buttons across the top of the screen take you to different sections for presets, synth (parameters and macros), sensitivity (MPE and aftertouch controls) and playing (mostly just for the arpeggiator at the moment). Then to the left of the screen there are two encoders for navigating the submenus, and the four knobs below control whatever option is listed above them on the screen. So, no, you’re not going to be doing a lot of live tweaking, but you also won’t spend 30 minutes trying to dial in a patch.

Part of the reason you won’t spend 30 minutes dialing in a patch is because there really isn’t much to dial in. The engine driving the Osmose is Haken Audio’s EaganMatrix and Expressive E keeps most of it hidden behind six macro controls. In fact, you can’t really design a patch from scratch — at least not the synth directly. You need to download the Haken Editor, which requires Max (not the streaming service), to do serious sound design. Then you need to upload your new patch to the Osmose over USB. Other than that, you’re stuck tweaking presets.

Expressive E Osmose macro controls.
Terrence O'Brien / Engadget

This isn’t necessarily a bad thing because, frankly, EaganMatrix feels less like a musical instrument and more like a PHD thesis. It is undeniably powerful, but it’s also confusing as hell. Expressive E even describes it as “a laboratory of synthesis,” and that seems about right; patching in the EaganMatrix is like doing science. Except, it’s not the fun science you see on TV with fancy machines and test tubes. Instead it’s more like the daily grind of real life science where you stare at a nearly inscrutable series of numbers, letters, mathematical constants and formulas.

I couldn’t get the Osmose and Haken Editor to talk to each other on my studio laptop (a five-year-old Dell XPS), though I did manage to get it to work on my work-issue MacBook. That being said, it was mostly a pointless endeavor. I simply can’t wrap my head around the EaganMatrix. I was able to build a very basic patch with the help of a tutorial, but I couldn’t actually make anything usable.

Hacken Editor and the EaganMatrix connected to the Osmose over USB.

There are some presets available on Patchstorage, but the community is nowhere near as robust as what you’d find for the Organelle or ZOIA. And, it’s not obvious how to actually upload those handful of presets to the Osmose. You can drag and drop the .mid files you download to the empty slots across the top of the Haken Editor and that will add them to the Osmose's user presets. But you wont actually see that reflected on the Osmose itself until you turn it off and turn it back on.

Honestly, many of the presets available on Patchstorage cover the same ground as 500 or so factory ones that ship with the Osmose. And it’s while browsing those hundreds of presets that both the power and the limitations of the EaganMatrix become obvious. It’s capable of covering everything from virtual analog, to FM to physical modeling, and even some pseudo-granular effects. Its modular, matrix-based patching system is so robust that it would almost certainly be impossible to recreate physically (at least without spending thousands of dollars).

Now, this is largely a matter of taste, but I find the sounds that come out of this obviously over-powered synth often underwhelming. They’re definitely unique and in some cases probably only possible with the EaganMatrix. But the virtual analog patches aren’t very “analog,” the FM ones lack the character of a DX7 or the modern sheen of a Digitone, and the bass patches could use some extra oomph. Sometimes patches on the Osmose feel like tech demos rather than something you’d actually use musically.

Expressive E Osmose preset menus with the Acid Bass patch highlighted.
Terrence O'Brien / Engadget

That’s not to say there’s no good presets. There are some solid analog-ish sounds and there are a few decent FM pads. But it’s the physical modeling patches where EaganMatrix is at its best. They definitely land in a kind of uncanny valley, though — not convincing enough to be mistaken for the real thing, but close enough that it doesn’t seem quite right coming out of a synthesizer.

Still, the way tuned drums and plucked or bowed strings are handled by Osmose is impressive. Quickly tapping a key can get you a ringing resonant sound, while holding it down mutes it. Aftertouch can be used to trigger repeated plucks that increase in intensity as you press harder. And bowed patches can be smart enough to play notes within a certain range of each other as legato, while still allowing you to play more spaced out chords with your other hand. (This latter feature is called Pressure Glide and can be fine tuned to suit your needs.)

The level of precision with which you can gently coax sound out of some presets with the lightest touch is unmatched by any synth or MIDI controller I’ve ever tested. And that becomes all the more shocking when you realize that very same patch can also be a percussive blast if you strike the keys hard.

Expressive E Osmose logo close up.

But, at the end of the day, I rarely find myself reaching for Osmose — at least not as a synthesizer. I’ve been testing one for a few months now, and while I have used it quite extensively in my studio, it’s been mostly as a controller for MPE-enabled soft synths like Arturia’s Pigments and Ableton’s Drift. It’s undeniably one of the most powerful MIDI controllers on the market. My one major complaint on that front being that its incredible arpeggiator isn’t available in controller mode.

The Osmose is a gorgeous instrument that, in the right hands, is capable of delivering nuanced performances unlike anything else. Even if, at times, the borrowed sound engine doesn’t live up to the keyboard’s lofty potential.

This article originally appeared on Engadget at

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