KeyCaster: Keys to MIDI

Novaryn

About this app

SynthBridge KeyCaster MIDI turns a USB or Bluetooth computer keyboard into a low-latency MIDI controller for Android. Play notes, trigger drums, launch chords and send MIDI CC from the keyboard you already own.

Use it with SynthBridge or any Android music app that accepts a MIDI input device. Select "SynthBridge KeyCaster" as the input, pick a preset, and your key presses are routed as MIDI messages with sub-5 ms latency.

🎹 PLAY NOTES WITH YOUR KEYBOARD
No more tiny on-screen piano. KeyCaster lets you use a real full-size keyboard — the one already on your desk — as a MIDI controller. Works with any standard USB (OTG) or Bluetooth HID keyboard.

🎛 FIVE BUILT-IN PRESETS
• Piano — QWERTY row mapped to a 2-octave C major scale (classic DAW keyboard layout)
• Drum Pad 4×4 — 16 keys trigger a full GM drum kit like an MPC
• DJ Controller — Function and number keys send MIDI CC for volume, filter and effects
• Combo — Number row plays drums, QWERTY plays piano, modifier keys drive CC
• Chord Pack — One key = one chord, with diatonic triads and 7th chords in C major

🛠 CUSTOM MAPPINGS
Create your own presets from scratch, duplicate a built-in to tweak, or import mappings shared by a friend. Every key can trigger a Note, a Chord (multiple notes at once), a Control Change (momentary or toggle), a Program Change, or a Pitch Bend. Capture any key with one tap; adjust channel, note, velocity and mode with sliders.

🔊 WORKS WITH ANDROID MIDI APPS
KeyCaster registers as a virtual MIDI input device named "SynthBridge KeyCaster" in the system. MIDI-capable synths, DAWs, samplers and sound modules can receive it:
• SynthBridge, the companion mobile sound module
• Android DAWs and MIDI hosts
• Synth and sampler apps that accept Android MIDI input

🎚 LIVE VELOCITY CONTROL
A global velocity slider on the home screen drives the velocity of every built-in preset in real time — add expression without editing a single mapping.

📲 KEEPS PLAYING IN THE BACKGROUND
Enable the accessibility service and KeyCaster will keep reading your keyboard while your DAW is in the foreground. Notification-shade shortcuts let you cycle between presets without leaving the app you are recording in.

👀 VISUAL KEYBOARD DIAGRAM
The on-screen keyboard layout highlights which keys are mapped to what — Note, Chord, CC, Program Change, Pitch Bend — with distinct colours, and lights up each key as you press it. Tap any key to inspect or edit its mapping.

📦 IMPORT / EXPORT PRESETS
Share mappings as simple JSON files via any file picker. Perfect for backing up your custom rig or passing a setup between devices.

🚀 ULTRA-LOW LATENCY
Built on Android's native MIDI framework (android.media.midi). Key event to MIDI byte in under 5 ms — good enough for live playing.

🔒 PRIVACY
All keyboard processing happens on device. No data leaves your phone. No account, no ads.

★ PART OF THE SYNTHBRIDGE SERIES
KeyCaster is designed to pair with SynthBridge, our mobile MIDI sound module that turns your phone into a 261-instrument sound source. Both apps work standalone — use KeyCaster with any MIDI-capable app you like.

Minimum Requirements:
• Android 7.0 (API 24) or higher
• External keyboard via USB OTG or Bluetooth HID

Permissions:
• Accessibility service (optional, for background keyboard capture)
• Post notifications (Android 13+, for the preset-switch shortcut)
• Foreground service (keeps the shortcut notification alive while you are in other apps)

From novaryn. Part of the SynthBridge series.