diff --git a/sequencer/build.sh b/sequencer/build.sh
index f335e80ba4166372358564725d9aaf0d3bac3af5..90ab43a0b005651e74d89007766b912531933fbe 100755
--- a/sequencer/build.sh
+++ b/sequencer/build.sh
@@ -1,4 +1,94 @@
 #!/bin/sh
 set -e
 cd "$(dirname "$0")"
-swift build -c release
+
+CONFIG=release
+APP=Sequencer.app
+BIN=Sequencer
+
+swift build -c "$CONFIG"
+
+# (Re)build the .app bundle from scratch so stale files never linger.
+rm -rf "$APP"
+mkdir -p "$APP/Contents/MacOS" "$APP/Contents/Resources"
+
+cp ".build/$CONFIG/$BIN" "$APP/Contents/MacOS/$BIN"
+
+cat > "$APP/Contents/Info.plist" <<'PLIST'
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleName</key>
+	<string>Sequencer</string>
+	<key>CFBundleDisplayName</key>
+	<string>Clover Sequencer</string>
+	<key>CFBundleExecutable</key>
+	<string>Sequencer</string>
+	<key>CFBundleIdentifier</key>
+	<string>com.clover.Sequencer</string>
+	<key>CFBundlePackageType</key>
+	<string>APPL</string>
+	<key>CFBundleShortVersionString</key>
+	<string>1.0</string>
+	<key>CFBundleVersion</key>
+	<string>1</string>
+	<key>LSMinimumSystemVersion</key>
+	<string>14.0</string>
+	<key>NSHighResolutionCapable</key>
+	<true/>
+	<key>NSPrincipalClass</key>
+	<string>Sequencer.SeqApplication</string>
+	<key>CFBundleDocumentTypes</key>
+	<array>
+		<dict>
+			<key>CFBundleTypeName</key>
+			<string>Sequencer Project</string>
+			<key>CFBundleTypeRole</key>
+			<string>Editor</string>
+			<key>LSHandlerRank</key>
+			<string>Owner</string>
+			<key>LSTypeIsPackage</key>
+			<true/>
+			<key>NSDocumentClass</key>
+			<string>Sequencer.ProjectDocument</string>
+			<key>LSItemContentTypes</key>
+			<array>
+				<string>com.clover.sequencer.project</string>
+			</array>
+			<key>CFBundleTypeExtensions</key>
+			<array>
+				<string>sq</string>
+			</array>
+		</dict>
+	</array>
+	<key>UTExportedTypeDeclarations</key>
+	<array>
+		<dict>
+			<key>UTTypeIdentifier</key>
+			<string>com.clover.sequencer.project</string>
+			<key>UTTypeDescription</key>
+			<string>Sequencer Project</string>
+			<key>UTTypeConformsTo</key>
+			<array>
+				<string>com.apple.package</string>
+			</array>
+			<key>UTTypeTagSpecification</key>
+			<dict>
+				<key>public.filename-extension</key>
+				<array>
+					<string>sq</string>
+				</array>
+			</dict>
+		</dict>
+	</array>
+</dict>
+</plist>
+PLIST
+
+# Mark the bundle as an app package for Finder/Launch Services.
+printf 'APPL????' > "$APP/Contents/PkgInfo"
+
+codesign --force --deep --sign "Sequencer Dev" "$APP"
+
+echo "Built $APP"