diff --git a/.swiftpm/xcode/xcshareddata/xcschemes/play-date.xcscheme b/.swiftpm/xcode/xcshareddata/xcschemes/play-date.xcscheme
deleted file mode 100644
index 4f0451d..0000000
--- a/.swiftpm/xcode/xcshareddata/xcschemes/play-date.xcscheme
+++ /dev/null
@@ -1,86 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<Scheme
-   LastUpgradeVersion = "2700"
-   version = "1.7">
-   <BuildAction
-      parallelizeBuildables = "YES"
-      buildImplicitDependencies = "YES"
-      buildArchitectures = "Automatic">
-      <BuildActionEntries>
-         <BuildActionEntry
-            buildForTesting = "YES"
-            buildForRunning = "YES"
-            buildForProfiling = "YES"
-            buildForArchiving = "YES"
-            buildForAnalyzing = "YES">
-            <BuildableReference
-               BuildableIdentifier = "primary"
-               BlueprintIdentifier = "play-date"
-               BuildableName = "play-date"
-               ReferencedContainer = "container:">
-            </BuildableReference>
-         </BuildActionEntry>
-      </BuildActionEntries>
-   </BuildAction>
-   <TestAction
-      buildConfiguration = "Debug"
-      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
-      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
-      shouldUseLaunchSchemeArgsEnv = "YES"
-      shouldAutocreateTestPlan = "YES">
-      <Testables>
-         <TestableReference
-            skipped = "NO">
-            <BuildableReference
-               BuildableIdentifier = "primary"
-               BlueprintIdentifier = "PlayDateTests"
-               BuildableName = "PlayDateTests"
-               ReferencedContainer = "container:">
-            </BuildableReference>
-         </TestableReference>
-         <TestableReference
-            skipped = "NO">
-            <BuildableReference
-               BuildableIdentifier = "primary"
-               BlueprintIdentifier = "PlayDateTests"
-               BuildableName = "PlayDateTests"
-               ReferencedContainer = "container:">
-            </BuildableReference>
-         </TestableReference>
-      </Testables>
-   </TestAction>
-   <LaunchAction
-      buildConfiguration = "Debug"
-      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
-      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
-      launchStyle = "0"
-      useCustomWorkingDirectory = "NO"
-      ignoresPersistentStateOnLaunch = "NO"
-      debugDocumentVersioning = "YES"
-      debugServiceExtension = "internal"
-      allowLocationSimulation = "YES"
-      queueDebuggingEnabled = "No">
-   </LaunchAction>
-   <ProfileAction
-      buildConfiguration = "Release"
-      shouldUseLaunchSchemeArgsEnv = "YES"
-      savedToolIdentifier = ""
-      useCustomWorkingDirectory = "NO"
-      debugDocumentVersioning = "YES">
-      <MacroExpansion>
-         <BuildableReference
-            BuildableIdentifier = "primary"
-            BlueprintIdentifier = "play-date"
-            BuildableName = "play-date"
-            ReferencedContainer = "container:">
-         </BuildableReference>
-      </MacroExpansion>
-   </ProfileAction>
-   <AnalyzeAction
-      buildConfiguration = "Debug">
-   </AnalyzeAction>
-   <ArchiveAction
-      buildConfiguration = "Release"
-      revealArchiveInOrganizer = "YES">
-   </ArchiveAction>
-</Scheme>
diff --git a/Sources/PlayDate/Sound.swift b/Sources/PlayDate/Sound.swift
index 87dff3c..fcb7b08 100644
--- a/Sources/PlayDate/Sound.swift
+++ b/Sources/PlayDate/Sound.swift
@@ -78,7 +78,9 @@ extension Sound {
     /// Removes a source from its channel.
     @discardableResult
     public static func removeSource(_ source: Source) -> Bool {
-        snd.removeSource.unsafelyUnwrapped(source.pointer) != 0
+        let removed = snd.removeSource.unsafelyUnwrapped(source.pointer) != 0
+        CallbackSource.release(source)
+        return removed
     }
 
     /// Sets a callback that records microphone input. Return `false` from the
@@ -196,6 +198,11 @@ extension Sound {
         deinit {
             if isOwned {
                 Channel.api.freeChannel.unsafelyUnwrapped(pointer)
+                // The freed channel no longer pulls its callback sources, so
+                // their trampoline registrations can be released too.
+                for source in retainedSources where source is CallbackSource {
+                    CallbackSource.release(source)
+                }
             }
         }
 
@@ -240,6 +247,7 @@ extension Sound {
         public func removeSource(_ source: Source) -> Bool {
             let removed = Channel.api.removeSource.unsafelyUnwrapped(pointer, source.pointer) != 0
             retainedSources.removeAll { $0 === source }
+            CallbackSource.release(source)
             return removed
         }
 
diff --git a/Sources/PlayDate/SoundSource.swift b/Sources/PlayDate/SoundSource.swift
index ebbda1b..848f761 100644
--- a/Sources/PlayDate/SoundSource.swift
+++ b/Sources/PlayDate/SoundSource.swift
@@ -66,10 +66,17 @@ extension Sound {
 
         let callback: Callback
 
-        /// Sources created through the top-level `Sound.addSource` are kept
-        /// alive here until removed with `Sound.removeSource`.
+        /// Every callback source is kept alive here while the C side may
+        /// still invoke its trampoline: from creation until it is removed
+        /// with `Sound.removeSource`/`Channel.removeSource`, or until its
+        /// owning channel is freed.
         nonisolated(unsafe) static var live: [CallbackSource] = []
 
+        /// Releases the registration added by `adopt(pointer:)`.
+        static func release(_ source: Source) {
+            live.removeAll { $0 === source }
+        }
+
         init(callback: @escaping Callback) {
             self.callback = callback
             super.init(pointer: nil, isOwned: false)