# Hex MIDI: Isomorphic Keyboard — Microtonal & Xenharmonic Synth

> Microtonal & Xenharmonic Synth (iPhone/iPad app by Trung Dung Hoang.)

- Source: https://appshunter.io/ios/app/hex-midi-isomorphic-keyboard/id6771364879 (this page in markdown: same URL + `.md`)
- Developer: [Trung Dung Hoang](https://appshunter.io/developer/1896778927)
- Category: Music, Education
- Price: Free with in-app purchases
- Age rating: 4+
- Requires: iOS 17.0 · 95 MB
- Languages: American English
- Released: 2026-08-28
- Data updated: 2026-10-04
- User reviews in markdown: https://appshunter.io/ios/app/hex-midi-isomorphic-keyboard/id6771364879/reviews.md

## What is Hex MIDI?

Hex MIDI is an isomorphic MIDI controller and microtonal synthesizer. Instead of the standard piano keyboard, notes are arranged in geometric hexagonal grids - meaning chord shapes, scales, and intervals remain identical across every key.

Whether you want to play alternative keyboards like the Wicki-Hayden or Jankó, compose in 19-EDO / 31-EDO microtonal tunings, or control your DAW over MIDI and MPE, Hex MIDI gives you the tools to explore harmony through geometry.

Built-In Keyboard Layouts:
• Wicki-Hayden – Classic concertina layout with fifths/fourths diagonals and octave columns.
• Jankó (Classic & Vertical) – Whole-tone rows with uniform chord fingerings.
• Harmonic Table – Euler's Tonnetz grid: major/minor third diagonals with vertical fifths for visual chord building.
• Bosanquet-Wilson (Maupin) – Generalized flat-top hex layout built for microtonal navigation.
• Harpejji – Whole-tone string layout with semitone vertical progression.
• Chromatic Button Accordion – Authentic C-System and B-System (Bayan) layouts.
• Fourths & Fifths – String instrument tunings for guitarists, bassists, and violinists.
• Major Thirds & Diminished Harmonica – Symmetrical grid layouts.
• Custom Layout Editor – Build and save your own hexagonal or rectangular grids.

Microtonal & Tuning Engine:
• EDO Presets: 19-EDO, 22-EDO (Shruti), 24-EDO (Quarter-tone / Maqam), 31-EDO (Meantone), 41-EDO, 53-EDO, and sub-12 tunings (5-EDO Slendro, 7-EDO, 10-EDO).
• Scale Formats: Bohlen-Pierce (13-EDT), Just Intonation, and custom scale generation.
• Scala Support: Import standard .scl tuning files and .kbm keyboard mappings.
• Visual Color Modes: 5ths spiral color coding, Tonnetz harmonic spectrum, and minimal two-tone palettes.
• Note Labels: Display note names with arrow accidentals, Solfège, interval numbers, or exact Hz.

MIDI & Expressive Performance:
• MIDI I/O: Connect via USB MIDI to hardware synthesizers, external keyboards, and DAWs (Ableton, Logic, Reaper, Bitwig).
• MPE & Vibrato: Per-note microtonal pitch-bend routing and touch vibrato.
• MTS Support: Real-time MIDI Tuning Standard SysEx transmission for compatible synths.
• Touch Control Pads: Integrated dual X/Y pads for assignable pitch, modulation, and CC filters.
• Built-In Sound Engine: High-fidelity soundfont player with instant response.

## Pricing and in-app purchases

Base price: Free.

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| Hex MIDI Pro | $12.99 | one-time |



## Version history (last 2 releases)

### 1.0.1 — 2026-09-24

• Microtonality Engine: Built-in scale builder, Scala (.scl/.kbm) import, expanded presets (19/22/24/31/41/53-EDO and microtonal note labels.
• New Layouts: Bosanquet, Perfect 5ths, B System Button Accordion, Diminished Harmonica layouts
Touch Enhancement: Vibrato and Velocity control
• Adaptive HUD: Dynamic display cutout/notch detection and layout switcher pill.
• Harmonic Color Schemes: Added Spiral of 5ths, Harmonic 5th, Neutral 3-Tier, and Two-Tone Minimalist Slate color modes.

### 1.0 — 2026-08-28

No release notes.

## Apps similar to Hex MIDI

| App | Rating | Price | Category |
| --- | --- | --- | --- |
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| [Rubberband: Microtonal Synth](https://appshunter.io/ios/app/rubberband-microtonal-synth/id6781069946) | — | Free | Music |
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| [GridStep](https://appshunter.io/ios/app/gridstep/id6756443258) | 5.0 (3) | $3.99 | Music |
| [Harpejii Instrument](https://appshunter.io/ios/app/harpejii-instrument/id6744958381) | 1.0 (2) | Free | Music |
| [Fingerophone: Touch Synth](https://appshunter.io/ios/app/fingerophone-touch-synth/id6784870429) | — | Free | Music |

## Related topics

[tonnetz](https://appshunter.io/ios/topics/tonnetz) · [huion keydial](https://appshunter.io/ios/topics/huion-keydial) · [rhythmic keyboard](https://appshunter.io/ios/topics/rhythmic-keyboard) · [isotope midi keyboard](https://appshunter.io/ios/topics/isotope-midi-keyboard) · [musical autoharp](https://appshunter.io/ios/topics/musical-autoharp)

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-10-04.*