Glass Bead Game III (GBG III) is an instrument for playing in just intonation on iPad and Mac. A sustained drone holds a reference pitch, and you move tones around it on a map of exact, whole-number frequency ratios — with an Apple Pencil, your finger, a keyboard or a mouse. It has its own built-in synth and can also send MPE MIDI to outboard synths, Eurorack and other apps.

Requirements

  • iPad with iPadOS 17.2 or later, or a Mac with macOS 14.2 or later
  • Apple Pencil recommended on iPad; a keyboard and mouse work on both
  • Free. No account, no ads, no in-app purchases.

Common questions

I don’t hear anything. Check the device’s volume first, then make sure Use internal synth is on in Settings (the gear button).

My MIDI synth plays in the wrong octave, or bends too far or not far enough. The synth’s pitch bend range doesn’t match GBG III’s. Set Pitch Bend Range in Settings to match your synth (±24 or ±48), or set the synth by hand. Verify Pitch Bend Range plays a true fifth and octave so you can check by ear. See the manual’s MIDI section.

Something is stuck sounding. Press the red Panic button.

Apple Pencil Pro squeeze doesn’t toggle Pedal. In the iPad’s own Settings → Apple Pencil → Squeeze, choose anything other than “Run Shortcut”.

Why does my Mac ask for microphone access? Only when you connect an iPad over USB using macOS’s Inter-Device Audio & MIDI (IDAM). macOS treats that connection as an audio device, so it asks. GBG III never records audio.

Why does my iPad ask for Local Network access? Only if you turn on Enable Network MIDI, which connects to MIDI gear and apps on your own Wi-Fi.

Contact

Questions, bug reports and suggestions are welcome. Email norm@sohl.com. I’m one person, so it may take a few days, but I read everything. It helps to say which device and system version you’re using, and what MIDI gear (if any) is connected.