Musicalculator

Musicalculator is a SwiftUI iOS calculator that turns keypad input into playable musical sequences. It combines a free-play instrument, a grid-based song editor, saved files, and a standard calculator in one Liquid Glass interface.

Features

• Free play: every supported keypad button plays its bundled sound immediately.
• Write Notes mode: records notes, rests, and operators into a grid. It is off by default.
• Sequence playback: starts at the cursor, or from the beginning when the cursor is at the end.
• Moving playback cursor: follows the sequence while it plays.
• Inline tempo changes: BPM values appear in the strip beneath a cell and take no grid space.
• Sharp notes: hold . while pressing a note or audible operator to shift it up one semitone.
• Compressed rests: consecutive blanks share one cell and display a small ×N count.
• Undo and redo: available from the expandable editor controls.
• Saved songs: name, save, save as, reopen, play, and delete compositions.
• Calculator: standard arithmetic with the same musical button feedback.
• Silent-mode audio: uses an iOS playback audio session, so sounds play while the mute switch is enabled.
• Low-latency playback: MP3s are decoded at launch and played through a pre-warmed voice pool.

Composition controls

Open Musicalculator and enable Write notes to record keypad input.

Input	Grid behavior
1–9	Inserts a note
Hold . + note	Inserts a sharp note such as .6 in one cell
+, −, ×, ÷, =	Inserts an operator event
Hold . + audible operator	Inserts a sharp operator such as .+ or .×
0, 00, %	Inserts a rest/blank
⌫	Removes the event before the cursor

Tap a grid cell to place the cursor at that event. New input is inserted at the cursor.

The upward chevron beneath the grid reveals:

• Tempo
• Undo
• Redo

Choose Tempo to adjust the BPM at the cursor in increments of five. A tempo marker is rendered in the narrow strip beneath its cell. The first cell defaults to 90. If a marker is adjusted back to the previous tempo, the redundant marker removes itself automatically.

Navigation

The leading toolbar menu is a native floating menu with:

• New Song — resets the current composition and editor state
• Play — opens the composer/free-play screen
• My Files — shows saved compositions
• Calculator — opens the standard calculator

When a composition contains playable events, Play/Stop and Save controls appear in the trailing navigation bar. Opening or saving a named file shows that name in the title bar. Tapping Save writes back to the current file; long-pressing Save shows a native menu with Save As… to create a new file.

Audio

Audio files live in Musicalculator/Sounds. Notes 1–9 and the supported operators each use their corresponding MP3 file.

Playback is built with AVAudioEngine and AVAudioUnitTimePitch:

• Twelve voices are connected and warmed at startup.
• Sound files are decoded into PCM buffers before the first key press.
• Sharp events use a pitch shift of exactly +100 cents.
• Pitch shifting does not change sample duration.

Persistence

Saved songs are encoded with Codable and stored in UserDefaults. Each file includes its sequence tokens and inline tempo events. Tempo is not stored as one global song setting. Saving an already-open file updates that same stored item instead of creating a duplicate.

Requirements

• macOS with Xcode 27.1 or later and the iOS 27.1 SDK or later
• iOS 26.5 or later
• Swift 5

iPhone Duo layouts

On iOS 27.1 and later, the composer and keypad share a native SwiftUI ArrangementView:

• Wide layouts place the composer on the left and keypad on the right, with manual resizing disabled.
• Unfolded portrait retains the adjustable composer height. Folding locks the split and lets the system place both panels clear of its reserved hinge region.
• Returning to unfolded portrait restores the preferred composer height instead of retaining a compact display's temporary height limit.
• Pose changes use standard SwiftUI animations and honor Reduce Motion. Direct handle dragging remains unanimated.
• The title is hidden when the system uses a vertical toolbar (including outer portrait and inner landscape), and in compact vertical size classes. Navigation, playback, and saving remain available.

The system handles split placement and asymmetric safe areas; the app does not infer a hinge from screen dimensions or device names. iOS 26.5 retains the stacked layout.

Design references: Apple's Design for iPhone Duo, adaptive layout demo, and toolbar guidance.

To check in Device Hub, exercise outer portrait, inner landscape (flat and folded), and inner portrait (flat and folded). Resize the composer before switching poses, verify that its height returns in flat portrait, and confirm that note entry, playback, and the Save button continue working. Also check Reduce Motion and Split View resizing.

Build and run

1. Open Musicalculator.xcodeproj in Xcode.
2. Select the Musicalculator scheme.
3. Choose an iPhone simulator or connected device.
4. Press Run.

Command-line build:

xcodebuild \
  -project Musicalculator.xcodeproj \
  -scheme Musicalculator \
  -destination 'generic/platform=iOS' \
  CODE_SIGNING_ALLOWED=NO \
  build

Tests

The test suite covers sequence tokens, sharp symbols, tempo timing, calculator behavior, audio-graph startup, and compact layout sizing. The toolbar UI regression repeatedly rotates the device and exercises navigation, Save As, and the first Save tap after a long press. Repeated physical fold/unfold transitions still require the Device Hub pose controls.

xcodebuild \
  -project Musicalculator.xcodeproj \
  -scheme Musicalculator \
  -destination 'platform=iOS Simulator,name=iPhone 17 Pro' \
  test

Project structure

Musicalculator/
├── AudioManager.swift       # Low-latency playback, pitch shifting, sequencing
├── ContentView.swift        # Navigation, composer, keypad, files, calculator UI
├── MusicModels.swift        # Tokens, saved songs, timing, calculator state
├── MusicalculatorApp.swift  # App entry point
├── Sounds/                  # Bundled note and operator MP3 files
└── Assets.xcassets          # App assets