The ESI Xsynth is a breakthrough instrument that combines a polyphonic aftertouch keyboard, a powerful virtual-analog synth engine, and a professional audio/MIDI interface into one sleek, ultra-portable design. Built for modern musicians and producers, it’s designed to slip easily into a backpack while delivering studio-quality sound and expressive performance anywhere inspiration strikes.
With its slim aluminum body, versatile connectivity, and deep sound-shaping tools, the Xsynth is more than just a compact keyboard — it’s a complete creative hub for the stage, studio, or road.
What is Xsynth?
Xsynth is a 25-key, ultra-flat instrument that merges three roles:
Standalone synth (virtual-analog subtractive engine)
USB audio/MIDI interface (class-compliant)
Master keyboard (polyphonic aftertouch, DAW control)
ESI pitches it as a “musical sketchbook” that travels anywhere, works on its own or with a DAW, and can sit at the center of a minimalist setup.
Hardware & Design: Ultra-Flat, Road-Friendly
Physically, Xsynth is closer to a metal tablet than a typical mini-synth: roughly 387 × 148 × 27 mm and about ~634 g. The chassis feels solid enough to live in a backpack, and the low-profile encoders don’t snag. Keys are “full-size” in width, but with very short travel (~2 mm)—a necessary compromise for the form factor.
Controls & I/O
Expect compact encoders and rubberized “smart” buttons, plus a minimal display. Connections include USB-C (power + audio/MIDI), 3.5 mm TRS MIDI in/out, line/headphone out, and aux in—handy if you want to route/monitor external audio through the built-in interface.
Playability & Expressiveness: Poly Aftertouch on the Go
Polyphonic aftertouch at this size/price is rare and the headline feature here. Reviewers note it’s genuinely expressive, though the short key travel means pressure control can take practice. Still: being able to press individual notes for vibrato/brightness/FX depth from such a tiny board is a big win for mobile sessions.
Sound Engine: Small Body, Serious Synthesis
Under the hood is a digital subtractive engine with:
3 oscillators (classic waveforms plus more unusual material—yes, field recordings & percussive content)
10-voice polyphony
Multimode filter, 3 LFOs, 3 AHDSR envelopes
Mod matrix (up to 16 slots)
Ring mod, arpeggiator, glide, octave
Onboard FX (three slots) and EQ
512 patches (4×128)
Reality check: you can’t load your own samples—the engine draws on internal ROM/waveforms. If you want true sampler behavior, pair Xsynth with your DAW, not the internal synth.
Audio/MIDI Interface Built-In
Plug via USB-C and it behaves as a class-compliant audio/MIDI interface (24-bit, up to high sample rates) while simultaneously serving as keyboard + synth. That means one cable to your laptop/tablet for playing, recording the internal synth, and monitoring external sources. For mobile creators, this is where Xsynth separates from slim controllers.
DAW & Editor Workflow
ESI provides an editor (desktop/tablet) for deeper patching, curve tweaks, and housekeeping. For most users, the editor + encoders combo is the sweet spot: decent immediacy on-device, deeper dives off-device.
Real-World Impressions: What Reviewers & Early Users Say
Portability & build: “Toss-in-a-backpack” tough, with premium-feeling metal/plastic mix; encoders stay out of the way.
Keys & aftertouch: Expressive poly AT, but the 2 mm stroke is a love-it/learn-it situation. Expect a different feel than a springy synth action.
Sound & features: The engine is richer than you’d expect at this size; mod matrix, FX, and arpeggiator invite real sound design, not just preset surfing.
UI trade-offs: With a compact panel there’s some menu-diving; not a dealbreaker, just part of the footprint.
Who It’s For
Perfect for:
Laptop producers who want a single device to play, record, and control on the go
Ambient/sound-design folks who’ll exploit poly aftertouch and the textural oscillator set
Live performers needing an ultra-portable backup synth/controller/interface
Verdict
The ESI Xsynth is more than just an ultra-thin keyboard — it’s a powerful all-in-one solution for modern music makers. By combining a polyphonic aftertouch keybed, a feature-rich synth engine, and a high-quality audio/MIDI interface into a sleek, travel-ready design, it sets itself apart as the ultimate companion for producers on the go.
Whether you’re sketching new ideas, performing live, or integrating it into your studio setup, the Xsynth offers a unique balance of portability, playability, and professional-grade sound. For musicians seeking a compact yet inspiring instrument that goes wherever creativity strikes, this little powerhouse more than delivers.










