Most MPE controllers arrive as finished products — a Seaboard, an Osmose, a LinnStrument, each with its own fixed playing surface. But some of the most interesting expressive-controller ideas are still coming from builders bolting existing gear together in ways manufacturers never intended. The latest example: the Ystring, a guitar-style MPE controller built by combining two Sensel Morph pads with overlays borrowed from the Joué Play controller.
What the Ystring Actually Is
The project, first documented by gearnews.com, pairs two Sensel Morph multi-touch surfaces mounted on a single board, using Joué's swappable silicone overlays to create a fretboard-like playing surface. The Morph's underlying technology is a pressure-sensitive touch matrix that already speaks MPE natively — it reports per-note position, pressure, and pitch bend, which is exactly the data a guitar-style instrument needs to feel expressive rather than like a strummed keyboard.
By splitting the surface across two Morphs and layering Joué's overlays on top, the build approximates a fretted neck: players can bend, slide, and apply pressure per string in a way that maps intuitively onto how a guitarist already thinks about the instrument, while still outputting standard MPE data that any compatible synth or plugin can receive.
Why the Sensel Morph Keeps Showing Up in DIY Builds
The Morph has become something of a favorite raw material for controller experiments, and it's easy to see why. Out of the box, the Morph is MPE-compatible across all of its Music Overlays, and it works with a wide range of MPE-aware plugins — Audio Damage Quanta, Madrona Labs Aalto, Arturia Pigments, and UVI Falcon among them. Its flat, borderless touch surface and interchangeable overlays make it unusually well-suited to being repurposed: unlike a keybed or a ribbon controller, a Morph's playing surface can be redefined entirely by swapping the overlay and remapping the software layer.
Joué's overlays bring a complementary strength — the company has always leaned into swappable, tactile silicone surfaces designed for different playing styles, from drum pads to string-like layouts. Combining the two effectively lets a builder mix Sensel's touch-sensing hardware with Joué's physical surface design language, without needing to build a control surface from scratch.
What This Says About the MPE Ecosystem in 2026
Builds like the Ystring are a useful signal for where expressive controller design still has room to grow. Commercial MPE hardware has matured a lot — Roli's Seaboard 2, Expressive E's Osmose, and Haken's Continuum all cover different corners of the keyboard-and-surface design space — but guitar-style MPE playing remains comparatively underserved by finished products. Projects like this fill that gap the way DIY synth builders have always filled gaps in commercial synthesizer lineups: by combining parts that already exist into something that doesn't.
It's also a reminder that MPE's real strength is as an open, well-documented standard rather than a single vendor's ecosystem. Because the Morph, Joué's overlays, and downstream MPE-compatible synths all speak the same per-note data format, a builder can mix hardware from entirely different companies and expect it to work together. That interoperability is precisely what the MIDI Polyphonic Expression specification was designed to enable back when it was ratified, and builds like the Ystring are a good demonstration of it paying off in practice, years later, in a form nobody at MIDI.org was necessarily picturing.
For players curious about guitar-style expressive playing, the Ystring isn't a product you can buy — it's a proof of concept. But as more builders publish their overlay files, mounting designs, and mapping configurations, don't be surprised if a commercial version of this idea shows up sooner rather than later.