J–17 · Poly synth $9.99 · Beta testing

Play a
sound nobody
else has.

One page of faders, four voices, no menus — a synth you can actually learn. Then feed it a recording you made in the world, and the keys play that as the voice.

Join the beta testing Why it exists
01Why it exists

Every preset you load, someone else already has

That's the quiet problem with software synths. You open a library of two thousand patches, scroll until something is close enough, and the sound you end up with is a sound anybody with the same download already owns. You picked it. You didn't make it.

J–17 fixes that at the source — literally. SPLICE takes any recording you have — a voice memo, a door hinge, a street, a phrase off your own guitar — and makes it the oscillator. The app listens first, tunes the keyboard to it, takes the attack into the envelope, and the splice arrives sounding like itself. Nobody else has your recording, so nobody else has your patch.

And it stays learnable. One page of faders, one slider per job, four voices, and a chorus you can hear working — no menus, no sub-pages, nothing hiding. You can see the entire instrument at once, which is why it teaches you what a filter actually does instead of asking you to trust a preset name.

“Every voice drifts ±1.8 cents — the vintage is built in, not a switch.”

— the J–17 field manual
02Heritage

Born of the Juno

INSPIRED BYRoland Juno-106 · JU-06A1984, AND THE BOUTIQUE REVIVAL

The Juno stays in the bones because the Juno works. What the phone adds is the museum problem solved: a Juno's oscillator is fixed forever; here it's whatever you recorded this morning. Wire the real JU in and its sliders drive this panel — two panels, one sound.

WHAT STAYS
  • One page of faders — DCO into filter into amp, nothing hidden
  • Four voices, one envelope each, oldest stolen — 1984 rules
  • The chorus wash where the Juno sound lives
  • The JU-06A's own CC chart, spoken 1:1, both directions
WHAT THE PHONE ADDS
  • SPLICE — any recording you caught in the world becomes the oscillator
  • The family's pattern grid, wired for notes
  • A rolling four-minute tape and one-button exports
  • Patches as plain files — AirDrop them, shelve them, print the paper patch sheet

Not a re-creation — a continuation. If you love the hardware, you'll feel at home here; learn here, and the hardware will feel like home too.

03The field manual

Splice. Shape. Pattern. Tape.

The splice

The second source. Import any recording, set IN and OUT, commit. The app listens first — it hears the recording's pitch and tunes the keyboard to it. Loop rolls a window you dial in by ear; the seam never clicks. WOW is tape wander, GRIT is the old-sampler crush, WANDER sends the loop walking.

The panel

Vertical faders with 0–100 readouts that match the printed patch sheet. 24 dB lowpass — the voice of the instrument; RES rings the edge to the point of scream. HPF step 0 adds the low boost — the Juno bass secret. Chorus I is slow and wide, II faster and deeper, I+II the big wash. Off is honest mono.

The pattern

The family's own grid, wired for notes — learn it on the drums, play it here. Rows are keys, columns are 16ths. Four clicks count you in; quantize is past-biased, so running late never throws a hit ahead. It loops notes, not audio — change the patch and the pattern changes with it.

The hardware

Wire a JU-06A in and its sliders drive this panel 1:1, no mapping — two panels, one sound. The paper patch sheet prints every fader 0–100 so a sound made here can be dialed into the real hardware by hand. The phone loves the synth back.

The whole manual ships inside the app — tap the wordmark. One screen, no settings page, the keys never leave the bottom.

04How it's used

Patch to pattern to tape

  1. PATCHStep through your sounds, then the factory dozen. The dot on the LCD means edited since load.
  2. PLAYThirteen keys upright, twenty-five sideways, multi-touch with glissando — or any MIDI keyboard, or the JU itself.
  3. SHAPEDrag the faders; tap a section title and it opens big with the keys still under your hands, so you hear every move.
  4. PATTERNEight slots, one to eight bars, count-in of four. LINK plays the filled ones in order as a song.
  5. KEEPThe tape is always rolling the last four minutes. One button exports the WAV, the MIDI line, and the patch sidecar — who · what · when.
05In the kit

The kit's keyboard voice

THE CLOCK

Set EXT and J–17 falls in step with P–16's or T–6's clock; Ableton Link locks it to everything on the network. It keeps sounding in the background, mixing with the rest of the kit.

THE CRATE

The deck's crate key drops a cut straight onto T–6's FROM J–17 shelf. On the tape machine, J–17 also mounts as a patchbay instrument — the tape prints the clean digital out, no mic, no bleed.

THE SHELF

Name a sound and it's a file — AirDrop it, back it up, put it on the library's PATCHES shelf. L–1 can hand it back to the synth from any device. Loading is not keeping; SAVE is how it becomes yours.

THE REFEREE

The C labels name the sounding octave, range included — what S–7 would read. If the synth and the tuner disagree about pitch, the synth is wrong.

Also an Audio Unit — aumu · j17i — the full panel in the plugin window; move a fader in the app and a live AU retunes mid-note.

$9.99. Bought once, yours for good.

$9.99 on the App Store buys the synth for iPhone and iPad. On the desk it’s $29.99 for the Mac app and AUv3 — or $79 for the whole Rack. No subscription, works offline. What you pay builds the next machine.

$9.99 ON THE APP STORE
IPHONE IPAD
Bought once. No subscription, no unlocks, nothing expires.
$29.99 ON THE DESK
MAC APP AUv3
Buy it on its own, or all four in the Rack for $79. What's in the Rack →

$9.99 at release. Free to test right now — leave your email and we'll send you a build.

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Next on the bench D–65 Amp & effects One blackface Deluxe, modeled deep, and a board of pedals that stay yours.