Glass Bead Game III — User Manual

Glass Bead Game III is shortened to GBG III throughout this manual.

This manual is organized in increasing order of complexity: setup, then playing GBG III live, then the settings you’ll reach for occasionally, then connecting outboard MIDI gear.

1. Setup

Requirements

iPadOS 17.2 or later, or macOS 14.2 or later. GBG III runs natively on both.

Installing GBG III

Installs from the App Store, same as any other app — nothing special needed.

GBG III is free software. It doesn’t require an account, doesn’t ask you to sign in or sign up, has no in-app purchases or payments of any kind, and doesn’t track or transmit your data anywhere — it makes no network connections on its own. The one exception is entirely your choice: on iPad, Enable Network MIDI (§4) opens a local Wi-Fi connection for MIDI only, off by default, and only to devices on your own network. (On Mac, Network MIDI is set up in macOS’s own Audio MIDI Setup, not in GBG III.)

What GBG III is

GBG III is a touch- and pen-driven instrument for playing in just intonation — tuning built directly from whole-number frequency ratios, rather than the equal-tempered 12 notes a piano or guitar gives you. A sustained drone holds a reference pitch; up to three moving tones (X, Y, and Z) are voices you position freely around that drone, and the graph itself is a map of that space — every visible intersection is a specific, exact interval away from the root. Play by moving through the map instead of pressing fixed keys.

For the theory behind it — why just intonation, how the lattice is built, what the diamonds and scale limits mean mathematically — see MapTone.

On first launch, GBG III asks for nothing — no Bluetooth pairing prompt, and MIDI access needs no permission prompt on either platform for a normal outboard-MIDI or Network MIDI connection. It never records or touches audio input - the one exception is connecting a USB-attached iPad via macOS’s IDAM (Inter-Device Audio & MIDI): since IDAM exposes the iPad as a combined audio+MIDI interface, macOS gates it behind the same microphone permission as an actual microphone, and will show that system prompt the first time you use it, even though no audio is ever recorded. Audio output is on by default - if you don’t hear anything, check your device’s volume before anything else. You can start playing immediately.

2. Playing GBG III live

Touch and pen

Drag a finger or Apple Pencil anywhere on the main graph to play the X and Y tones together — your touch’s horizontal position sets X, vertical sets Y. Z has its own separate touch zone (the narrow slider alongside the graph), so you can hold a Z position with one hand while playing X/Y with the other — the standard two-handed setup is a pencil for X/Y in your dominant hand, a thumb on the Z-slider in the other.

Keyboard shortcuts

On Mac, your keyboard works immediately. On iPad, connect a Bluetooth or USB keyboard (or a cheap keypad that emulates one) for the same shortcuts. Defaults:

There’s no separate toggle key for Pedal — the keyboard only offers the hold behavior above, matching a real damper pedal. To toggle Pedal on and leave it on, use the on-screen button (or, on iPad, Pencil squeeze — see below).

All of these are remappable — see Keyboard Mapping under Settings.

Mouse and trackpad

A mouse works the same on Mac and iPad (on iPad, connect any Bluetooth or USB mouse):

• Click and drag on the graph to play X and Y, or on the Z-slider to move Z — the same as a finger or pencil. On iPad, the pencil and touch keep working alongside the mouse; just don’t drive the graph with both at the same moment.
• Right button — Portamento, held (remappable in Keyboard Mapping, as is a middle button on iPad).
• Scroll wheel — steps Z up or down one scale degree per notch. On a Mac trackpad or Magic Mouse, a short swipe moves one step; on iPad, a mouse with a clicking wheel works best.

Apple Pencil Pro squeeze

On iPad with an Apple Pencil Pro, squeezing the pencil toggles the Pedal — a gesture on the same hand already holding the pencil, so it doesn’t compete with your other hand’s work on the Z-slider. If squeeze doesn’t seem to do anything, check Settings → Apple Pencil → Squeeze on the iPad itself: if it’s set to “Run Shortcut,” iPadOS intercepts the gesture before GBG III ever sees it. Any other setting works.

The on-screen controls

Drone, Portamento, Pedal, Panic, and Settings are also always reachable as buttons — in the window’s title bar on Mac, or as a column beside the graph on iPad (on whichever side isn’t currently hosting the Z-slider). Useful any time you’d rather tap than remember a key, or on iPad without a keyboard connected.

On iPad, this button column and the Z-slider always sit on opposite sides of the graph, so whichever hand isn’t holding the pencil has both within reach. Z-Slider Side under Settings (Left or Right) flips both together, to match whichever hand you actually play with.

Portamento — gliding between pitches

By default, touching the graph snaps to the nearest just-intoned scale degree — you always land precisely on a tuned pitch. Portamento turns that off, so pitch follows your touch continuously instead, letting you glide between pitches the way you’d slide a finger on a fretless instrument.

Two ways to use it:

• Toggle (G, H, or the button) — turns Portamento on or off for as long as you leave it that way, across as many touches as you like.
• Hold (Shift) — engages Portamento only while held, for a single glide in the middle of an otherwise-snapped phrase, then returns to whatever the toggle state was before you pressed it.

This is one of the two main real-time expressive tools, alongside Pedal — reach for it whenever you want continuous pitch motion instead of discrete steps.

Pedal — sustain

Pedal works like a piano’s damper pedal: it keeps whatever’s currently sounding held after you lift your touch, instead of cutting off the moment you release. That lets you let go of the graph entirely while a tone continues, or start a new touch replacing an already-sustained one.

• On Mac, Pedal is held (Space, F, or J) — press and hold like a real pedal, release to let the sound stop naturally.
• On iPad, Pencil squeeze and the on-screen button are both toggles instead — squeeze once to engage, again to release, since there’s no natural physical “hold” gesture for a squeeze. Squeeze only ever drives Pedal, never Portamento.
• A standard MIDI sustain pedal works too, with no setup on GBG III’s side: connect it through whatever’s set as your MIDI Source (see §4), and any incoming sustain-pedal message drives Pedal automatically, held-down/released just like Space bar - on any MIDI channel, not tied to X/Y/Z’s own channels.

Panic

If something ever gets stuck sounding, the red Panic button force-silences every voice immediately. A pure safety net — reach for it any time something doesn’t stop when you expect.

3. Settings

Settings is a popover reached from the gear icon (title bar on Mac, on-screen controls on iPad). Most of it is display/exploration, not performance-critical, so you’ll reach for these occasionally rather than mid-phrase.

• Diamonds — shows/hides the diamond markers at valid scale intersections. Turn it off for a cleaner, less cluttered view, especially with Dissonance Field on underneath.
• Dissonance Field — a continuous roughness/consonance visualization behind the grid. Turn it on when exploring unfamiliar harmonic territory and you want to see where the consonant regions are, not just the marked diamonds; leave it off otherwise to save a little rendering overhead.
• Filter Grid to Z — thins the background grid down to just the scale degrees relevant to your current Z position, matching how the diamonds themselves thin out. Turn it off if you’d rather see the full, uniform grid regardless of where Z sits.
• Note X / Note Y / Note Z — mutes an individual voice without hiding its crosshair. Use this to practice or explore one or two axes at a time, or to silence a voice you’re about to reposition before bringing it back in.
• Harmonics — picks the prime limit (3 through 19) that generates the scale. Lower limits give simpler, more consonant intervals; higher limits open up more exotic, complex ones. Change this to shift the harmonic character of everything available to play.
• View — Square, Diamond, or Triangle: different visual arrangements of the same pitch lattice. Mostly a presentation/exploration choice — try a different one to see the same structure from a different angle, or for a change of look when performing.
• Z-Slider Side — Left or Right. Moves the Z-slider (and, on iPad, the on-screen control column) to whichever side suits your grip - set this once for how you actually hold the device/pencil.
• Keyboard Mapping — see §2 above for what’s remappable.

4. Connecting outboard MIDI gear

MIDI output is controlled by Use Midi MPE in Settings (on by default). Everything in this section lives under that switch.

GBG III’s MIDI Destination and MIDI Source pickers (under Use Midi MPE) list whatever your Mac or iPad already sees as MIDI ports — physical USB-MIDI interfaces, virtual/IAC ports, Bluetooth MIDI devices, or Network MIDI sessions. GBG III draws no distinction between these: if your device already shows up in your Mac’s Audio MIDI Setup or your iPad’s Bluetooth settings, it’ll show up here too, listed by whatever name that device gives itself. There’s no separate in-app Bluetooth pairing screen — pair the device at the system level first.

• MIDI Destination is where GBG III sends pitch/note data to — an external synth, a Eurorack MIDI-to-CV interface, or another app (a DAW recording your performance live, on the same Mac or over USB/Network MIDI).
• MIDI Source is where GBG III listens for incoming MIDI from — an external controller, or a sequencer or DAW playing X/Y/Z back on their channels (2/3/4, see MPE below).
• Use internal synth — GBG III’s own built-in sound. Turn this off once your outboard gear is working and you’d rather hear only that.

Network MIDI (Wi-Fi)

• iPad: turn on Enable Network MIDI. Your iPad then appears as a Network MIDI session that a Mac on the same Wi-Fi can connect to in Audio MIDI Setup → Window → Show MIDI Studio, then the Network (globe) button (or a USB cable works too). Once connected, the session shows up in MIDI Destination and MIDI Source like any other port. iPadOS asks for Local Network permission the first time; if you declined, turn it back on in Settings → Privacy & Security → Local Network.
• Mac: there’s no switch in GBG III. Set up the session in Audio MIDI Setup’s MIDI Network Setup window, and it appears in GBG III’s pickers.

Sustain pedal

A standard MIDI sustain pedal (or any controller sending the sustain-pedal message, CC64) works as soon as it’s reachable through your chosen MIDI Source - no separate setting to turn on. It drives Pedal exactly like the Space bar: pedal down engages sustain, pedal up releases it. It isn’t tied to X/Y/Z’s own MIDI channels - a pedal sends this on whatever channel it’s configured for (often channel 1 by default), and GBG III watches for it on any incoming channel.

MPE

GBG III is MPE-only (MIDI Polyphonic Expression) — every voice (Drone/X/Y/Z) always gets its own MIDI channel with independent pitch bend; there’s no separate “plain MIDI” mode to turn on or off. This is safe for any receiver: MPE’s extra zone-declaration message is itself ordinary, backward-compatible MIDI, so gear that doesn’t understand it simply ignores that message and still receives normal per-channel note-on/off and pitch bend, exactly as it would from any multi-channel MIDI source.

Channel assignments: Drone/X/Y/Z use channels 5/2/3/4 — X/Y/Z occupy the first three (useful if your receiver only cares about your three main voices), Drone comes last, and channel 1 is reserved as the MPE zone’s master channel.

Pitch bend range

Pitch Bend Range (under Use Midi MPE) chooses ±24 semitones (the default) or ±48, the MPE standard’s own default. GBG III announces the chosen range to the receiver automatically with the standard MIDI RPN 0 message on every voice channel, and uses the same range to read incoming notes from your MIDI Source. Well-behaved gear picks this up on its own. Real analog/modular gear often doesn’t — if notes sound in the wrong octave or with a squashed/exaggerated bend, either set your instrument’s own pitch bend range by hand to match, or switch GBG III to whichever range your instrument already uses.

Tune Midi

For gear that has to be tuned by hand and can’t be retuned over MIDI (most modular/analog synths): press Tune Midi. This sounds all four voices at a straight 440 Hz (A) and tells you which MIDI channels are carrying it. Tune your instrument’s own oscillator by ear (or with a tuner) against that reference, then press Stop to return to normal playing.

Verify Pitch Bend Range

Even after setting your gear’s pitch bend range to match (above), it’s worth confirming the result actually sounds right — real gear doesn’t always respond exactly as declared. Use Unison / Fifth / Octave to sound all four voices together at those exact just-intonation intervals (not the tempered approximations most gear defaults to), and listen for whether your instrument’s actual response matches. Stop returns to normal playing.

Questions? See the support page or email norm@sohl.com.