An Android app that turns a tablet into pages of MIDI controls – 10 faders, 8 buttons, a two-octave keyboard, 16 MPC-style drum pads and 8 LFOs – sending MIDI Control Change (CC) and note messages over Wi-Fi via RTP-MIDI (AppleMIDI). Your computer sees the tablet as a regular MIDI input, e.g. in Ableton Live.
Settings screen
- Five Pages, switched with the tabs in the top bar:
- Faders: 10 vertical faders that glide to the touched position instead of jumping
- Buttons: 8 big buttons in two rows of 4
- Keyboard: 25 keys (two octaves, C to C) sending Note On/Note Off; chords and sliding across keys (glissando); Oct −/Oct + shift the range, shown in Ableton's note names (default C2–C4, i.e. notes 48–72)
- Pads: 4×4 MPC-style drum pads (rectangular, up to 1.6 times wider than tall, to use the screen width) sending Note On/Note Off on channel 10, laid out like an Ableton Drum Rack (notes 36–51, C1 bottom left); every touch retriggers (two-finger rolls), sliding onto other Pads does nothing
- LFOs: 8 LFOs that move a CC value up and down along a sine on their own. Each has an on/off button (with LED), a bar where you drag the Min and Max handles (Min above Max runs inverted) and a Speed of 0.2–120 s per cycle (drag up/down). LFOs keep running while you switch Pages, start switched off when the app starts, send at most 50 messages per second, and by default target CC 102–109 – overlapping with Controls is intended. Name, CC and channel are set in the settings
- Buttons are Momentary (on while held) or Latch (each press flips on/off); they send 127 for on, 0 for off. Latch Buttons have a small LED in the corner that lights while they are on
- 7-bit CC (0–127), send-only, landscape
- Every Control re-sends its final value shortly after release, and every Note Off is sent twice, to make up for lost Wi-Fi packets; held notes are released when you switch Pages or leave the app
- Per-Control Assignment (name, CC number, MIDI channel, and mode for buttons), plus Keyboard channel and velocity (default 100) and per-Pad name and note with a shared Pad channel and velocity, edited in the settings (gear icon), which have one tab per Page and open on the Page you are on; duplicate CC/channel combinations are flagged, also across Pages
- Default CCs: faders 20–29, buttons 110–117, LFOs 102–109, all on channel 1
- Advertises itself via Bonjour as Faderling plus the device model (e.g. Faderling KFAUWI), so several tablets can be told apart; the receiver starts the Session
- Session status shown on the main screen
- Keeps the screen on while a Page is shown (not on the settings screen, where the normal screen timeout applies); plug the tablet in for longer sessions
- Runs on Android 5.1 (API 22) and newer
- Works on phones too: on low screens (less than 450 dp high, e.g. a phone in landscape) the Keyboard shows one octave (C3–C4) with wider Keys; tablets keep two octaves
Get the signed APK from the latest release and install it on your tablet or phone (allow installing apps from unknown sources when Android asks). See CHANGELOG.md for what changed between versions.
Requires the Android SDK (ANDROID_HOME or local.properties with sdk.dir) and a JDK 17+.
.\gradlew.bat assembleDebug
adb install -r app\build\outputs\apk\debug\app-debug.apkDebug builds are installed as Faderling Debug (com.duddex.faderling.debug), so they can sit next to a release install.
A signed release build (.\gradlew.bat assembleRelease) needs the signing key, which is not part of the repository. The build reads its location and passwords from ~/.android/faderling-release.properties (or the file given with -Pfaderling.signing=<path>); without it, the release APK is built unsigned.
Unit tests and lint:
.\gradlew.bat testDebugUnitTest lintDebugEvery push and pull request is built by GitHub Actions; the debug APK can be downloaded from each run's artifacts.
- Install rtpMIDI by Tobias Erichsen.
- Start Faderling on the tablet (same Wi-Fi network as the PC).
- In rtpMIDI, create a session under My Sessions (+) and enable it.
- Select Faderling <model> (e.g. Faderling TB305FU) in the Directory list and click Connect. The tablet shows
Session: <PC name>. - In your DAW, enable the rtpMIDI session port as a MIDI input.
On macOS, use Audio MIDI Setup → MIDI Network Setup instead of rtpMIDI.
The Session only runs while Faderling is visible. It ends when the app is closed or restarted, when you switch to another app, or when the screen turns off (power button, or the screen timeout while you are on the settings screen); Faderling does no network activity in the background. Click Connect in rtpMIDI again afterwards.
This VCV Rack 2 patch shows the Faders, Buttons and LFOs Pages in action, using Faderling's default CC values. It only uses modules that come with VCV Rack (Core and Fundamental):
- Faders – a MIDI-CC to CV module receives CC 20–29 and drives 10 VCA-1 modules, whose level meters follow the faders.
- Buttons – a second MIDI-CC to CV module receives CC 110–117 and drives 8 Push modules, which light up while a button is on.
- LFOs – a third MIDI-CC to CV module receives CC 102–109 and drives 8 more VCA-1 modules, whose meters move with the running LFOs.
After opening the patch, select your rtpMIDI session port as the MIDI device in each of the three MIDI-CC to CV modules.
- Lenovo tablets (ZUI): pressing three Controls, Keys or Pads at once takes a screenshot. Lenovo's three-finger system gestures (swipe down = screenshot, swipe up, spread = split screen, …) are handled by the system before the app sees the touches, and apps cannot turn them off. Disable them on the tablet under Settings → System → Gestures (the exact menu depends on the ZUI version), or via ADB:
Other manufacturers have similar multi-finger gestures; disable them if they get in the way.
adb shell settings put system three_finger_slide_down_enabled 0
Python 3, standard library only:
tools/fader_monitor.py– shows every CC arriving on a MIDI input port (e.g. the rtpMIDI session port) as a fader. Windows only.python tools\fader_monitor.py --list python tools\fader_monitor.py "My Session"
tools/rtpmidi_probe.py– connects to the tablet directly as an RTP-MIDI initiator and prints received CC and note messages; useful without rtpMIDI.python tools\rtpmidi_probe.py <tablet-ip>
tools/latency_probe.py– measures the network latency to the tablet: 200 clock-sync round trips, then the send → arrival time of every MIDI packet while you play. It connects as its own Session, so rtpMIDI can stay connected.python tools\latency_probe.py <tablet-ip>
- GLOSSARY.md – domain language (Control, Fader, Button, Keyboard, Key, Pad, LFO, Page, Assignment, Session)
- docs/adr – architecture decisions
Faderling started with a simple question: is an old Amazon Fire tablet still good for anything? The Fire 7 from 2017 is stuck on Android 5.1, and many current apps no longer run on it. The first answer was a page of ten faders sending MIDI CC over Wi-Fi to a DAW – and it worked well enough that buttons, a keyboard, drum pads and LFOs followed. Faderling still runs on that Fire tablet today, and on current Android tablets and phones as well.
Faderling was developed with the help of a large language model (LLM). An AI coding assistant wrote most of the code, tests and documentation, following the requirements and design decisions of the project's author.