Haken Audio has long made the case that the keyboard is an accident of history rather than the best way to play an expressive electronic instrument. Its flagship Continuum Fingerboard proved that case to a generation of sound designers and MPE enthusiasts, but at nearly a meter wide and several kilograms heavy, it was never an instrument you'd casually toss in a backpack. That changes with the Slim 21 Continuum, unveiled ahead of SynthFest France 2026.
A Full Continuum, Shrunk Down
The Slim 21 covers a modest 21 half steps, just under two octaves, in a frame measuring 45 x 19 x 3 cm and weighing only 1.6 kg. That's a fraction of the footprint of the standard Continuum models, and it's light enough to travel in carry-on luggage. What hasn't been reduced is the engine underneath: the Slim 21 runs the same EaganMatrix Sound Engine found in Haken's larger instruments, meaning the synthesis architecture, patch library, and expressive capabilities are effectively unchanged.
Each finger position is tracked using up to 12 independent Hall-effect sensors, sampling pitch, pressure, and front-to-back movement hundreds of thousands of times per note. That density of tracking is what gives Continuum instruments their reputation for the kind of micro-expression more commonly associated with strings or woodwinds than with an electronic controller: true continuous pitch glide, individual note vibrato, and pressure-based timbral shaping that responds to the same kind of touch nuance a violinist or vocalist would use.
Why Size Matters for MPE Adoption
One of the recurring criticisms of high-end MPE hardware has been accessibility, not just price, but sheer practicality. A full-size Continuum or a Haken Slim keyboard is a serious commitment of studio real estate. The Slim 21's smaller footprint targets a different use case: a compact expressive voice that a keyboardist or sound designer can add to a live rig, a modular setup, or a writing session without dedicating a full desk to it. According to SonicState's Superbooth coverage, the instrument drew steady interest from performers looking for a "second voice" they could layer alongside conventional keyboards rather than replace them entirely.
Synthtopia's writeup and Synth Anatomy's review both frame the Slim 21 as the most portable full-size Continuum experience Haken has shipped to date, distinguishing it from cut-down or toy-like alternatives that sacrifice tracking resolution for size.
Pricing and Availability
The Slim 21 is priced at $1,799 USD, positioning it below Haken's larger Continuum models while remaining a premium purchase relative to mainstream MPE keyboards. Haken has said units typically ship within five weeks of payment, a lead time consistent with the company's small-batch, largely hand-built production process. Full specifications and ordering details are available directly from Haken Audio's Continuum Fingerboards page.
What It Means for MPE Players
For musicians already invested in the MPE ecosystem, the Slim 21 is notable less as a new instrument and more as a new form factor for an already-respected one. It lowers the physical and logistical barrier to owning a Continuum-class controller without touching the underlying sound engine that made the instrument a reference point for expressive synthesis in the first place. Combined with growing native MPE support in DAWs like Ableton Live and Bitwig Studio, compact hardware like the Slim 21 suggests the expressive controller market is maturing past its early "big and expensive" phase and into something closer to a practical, everyday tool for composers and performers.
Whether that translates into meaningfully broader adoption will depend on how the wider software ecosystem, from plugin instruments to DAW-native MPE editing, continues to lower the learning curve that has historically kept expressive controllers a niche pursuit.