M2DX

MIDI 2.0 + DX7-compatible FM Synthesizer

Join TestFlight Beta

Welcome to M2DX support.

M2DX is a MIDI 2.0-compatible DX7 FM synthesizer for iOS, delivering classic 6-operator / 32-algorithm FM tones reimplemented entirely in Swift 6. The synthesis engine is provided by the M2DX-Core library.

TestFlight Beta

iOS / iPadOS 18+ — install the public beta:

  1. Install Apple's TestFlight app from the App Store (one-time)
  2. On your iPhone / iPad, open testflight.apple.com/join/BAtGszPw
  3. Tap "Accept" → "Install"

Note: the very first install after Beta App Review approval may take 1–2 minutes (occasionally up to 24 hours) to propagate.

Current Status — Why TestFlight

M2DX is not yet at instrument-grade quality. We are publishing the public TestFlight beta with the constraints and untested items below, in order to gather feedback and iterate.

MIDI 2.0 coverage is limited

  • We have not been able to procure enough MIDI 2.0-capable hardware, so UMP behavior has only been verified across a limited set of device combinations
  • Differences in MIDI 2.0 support across macOS versions (CoreMIDI behavior, etc.) are not fully characterized
  • Vendor-specific extensions and proprietary profiles built on top of MIDI 2.0 have only been partially analyzed (specifically, parts of KORG's implementation); other vendors' proprietary implementations remain untouched

DX7 preset compatibility

  • 32 initial presets are bundled, but the tonal character compared to vintage FM has not been fully verified across all presets
  • Bank loading and SysEx patch import compatibility will be improved progressively across upcoming TestFlight builds

FX chain

  • The 6-stage FX chain (EQ → Drive → Chorus → Reverb → Stereo → Maximizer) is at the "working implementation" stage. Musical tuning of parameter ranges and endpoints, CPU efficiency, and interaction optimization are still ahead

If you spot bugs or oddities

Crashes are auto-reported via Firebase Crashlytics (see the Privacy Policy for details). Reproducible issues are easier to fix — if you can, please send a report to support@hakaru.net.

Features

Full MIDI 2.0 UMP Support

Native Universal MIDI Packet (UMP) decoding with 16-bit velocity (65,536 levels), 32-bit CC values, and 32-bit pitch bend for smooth, expressive control. MIDI 1.0 fallback is automatic.

DX7-Compatible FM Engine

A 6-operator / 32-algorithm DX7-style FM synthesis engine implemented in pure Swift. Int32 Q24 fixed-point arithmetic targets the character of vintage FM. 32 initial presets are bundled.

16-Voice Polyphony

16 simultaneous voices with sustain pedal (CC64) and pitch bend (±2 semitones) support. Padé-approximation tanh soft-clipping prevents digital distortion.

6-Stage FX Chain

EQ → Drive → Chorus → Reverb → Stereo → Maximizer signal chain. Every parameter can be MIDI Learn-mapped to any CC.

MIDI-CI Property Exchange

Exposes 155+ parameters in a hierarchical namespace. Compatible DAWs and controllers auto-discover parameters, with JSON-based preset management (no SysEx required) — a self-describing instrument.

Low Latency

AVAudioSourceNode direct rendering drives the FM engine inside the CoreAudio render callback, eliminating buffer-queueing overhead. The iOS IOBufferDuration (~5 ms) is the effective latency floor.

System Requirements

  • iOS / iPadOS 18+ (TestFlight beta available now)
  • macOS support is planned for the future

FAQ

"Install" is grayed out

Right after Beta App Review approval, propagation to TestFlight can take a while. Please try again after about 24 hours.

What happens if the app crashes?

Starting with v1.3.1 (build 5), Firebase Crashlytics auto-reports crashes. Reproducing a crash helps us identify and fix it quickly. See the Privacy Policy for details on the data we collect.

Can I load DX7 SysEx presets?

32 initial presets are built in. SysEx import for user-supplied banks will be announced in upcoming TestFlight builds.

Do I need a MIDI 2.0-compatible DAW?

No. MIDI 1.0 fallback is automatic, so any traditional MIDI controller or DAW works. A MIDI 2.0 environment unlocks higher-resolution expression.

Is M2DX available as an AUv3 plug-in?

Currently it ships as a standalone iOS / iPadOS app. AUv3 support is under consideration.

Links

Contact

For questions, bug reports, and feature requests, please reach out at:
support@hakaru.net