diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
index ac97ad808..bd78c6635 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
@@ -39,6 +39,7 @@
 		4B3BA0CF1D318B44005DD7A7 /* MOS6522Bridge.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4B3BA0C91D318B44005DD7A7 /* MOS6522Bridge.mm */; };
 		4B3BA0D01D318B44005DD7A7 /* MOS6532Bridge.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4B3BA0CB1D318B44005DD7A7 /* MOS6532Bridge.mm */; };
 		4B3BA0D11D318B44005DD7A7 /* TestMachine.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4B3BA0CD1D318B44005DD7A7 /* TestMachine.mm */; };
+		4B3F1B461E0388D200DB26EE /* PCMPatchedTrack.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B3F1B441E0388D200DB26EE /* PCMPatchedTrack.cpp */; };
 		4B44EBF51DC987AF00A7820C /* AllSuiteA.bin in Resources */ = {isa = PBXBuildFile; fileRef = 4B44EBF41DC987AE00A7820C /* AllSuiteA.bin */; };
 		4B44EBF71DC9883B00A7820C /* 6502_functional_test.bin in Resources */ = {isa = PBXBuildFile; fileRef = 4B44EBF61DC9883B00A7820C /* 6502_functional_test.bin */; };
 		4B44EBF91DC9898E00A7820C /* BCDTEST_beeb in Resources */ = {isa = PBXBuildFile; fileRef = 4B44EBF81DC9898E00A7820C /* BCDTEST_beeb */; };
@@ -482,6 +483,8 @@
 		4B3BA0CB1D318B44005DD7A7 /* MOS6532Bridge.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = MOS6532Bridge.mm; sourceTree = "<group>"; };
 		4B3BA0CC1D318B44005DD7A7 /* TestMachine.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = TestMachine.h; sourceTree = "<group>"; };
 		4B3BA0CD1D318B44005DD7A7 /* TestMachine.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = TestMachine.mm; sourceTree = "<group>"; };
+		4B3F1B441E0388D200DB26EE /* PCMPatchedTrack.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = PCMPatchedTrack.cpp; sourceTree = "<group>"; };
+		4B3F1B451E0388D200DB26EE /* PCMPatchedTrack.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = PCMPatchedTrack.hpp; sourceTree = "<group>"; };
 		4B44EBF41DC987AE00A7820C /* AllSuiteA.bin */ = {isa = PBXFileReference; lastKnownFileType = archive.macbinary; name = AllSuiteA.bin; path = AllSuiteA/AllSuiteA.bin; sourceTree = "<group>"; };
 		4B44EBF61DC9883B00A7820C /* 6502_functional_test.bin */ = {isa = PBXFileReference; lastKnownFileType = archive.macbinary; name = 6502_functional_test.bin; path = "Klaus Dormann/6502_functional_test.bin"; sourceTree = "<group>"; };
 		4B44EBF81DC9898E00A7820C /* BCDTEST_beeb */ = {isa = PBXFileReference; lastKnownFileType = file; name = BCDTEST_beeb; path = BCDTest/BCDTEST_beeb; sourceTree = "<group>"; };
@@ -1295,11 +1298,13 @@
 				4BAB62AB1D3272D200DF5BA0 /* Disk.cpp */,
 				4B6C73BB1D387AE500AFCFCA /* DiskController.cpp */,
 				4B30512B1D989E2200B4FED8 /* Drive.cpp */,
+				4B3F1B441E0388D200DB26EE /* PCMPatchedTrack.cpp */,
 				4BAB62B61D3302CA00DF5BA0 /* PCMTrack.cpp */,
 				4B0BE4271D3481E700D5256B /* DigitalPhaseLockedLoop.hpp */,
 				4BAB62AC1D3272D200DF5BA0 /* Disk.hpp */,
 				4B6C73BC1D387AE500AFCFCA /* DiskController.hpp */,
 				4B30512C1D989E2200B4FED8 /* Drive.hpp */,
+				4B3F1B451E0388D200DB26EE /* PCMPatchedTrack.hpp */,
 				4BAB62B71D3302CA00DF5BA0 /* PCMTrack.hpp */,
 				4BB697CF1D4BA44900248BDF /* Encodings */,
 				4BAB62B21D327F7E00DF5BA0 /* Formats */,
@@ -2367,6 +2372,7 @@
 				4B69FB441C4D941400B5F0AA /* TapeUEF.cpp in Sources */,
 				4BF829691D8F7361001BAE39 /* File.cpp in Sources */,
 				4BA61EB01D91515900B3C876 /* NSData+StdVector.mm in Sources */,
+				4B3F1B461E0388D200DB26EE /* PCMPatchedTrack.cpp in Sources */,
 				4B4DC8211D2C2425003C5BF8 /* Vic20.cpp in Sources */,
 				4BF8295D1D8F048B001BAE39 /* MFM.cpp in Sources */,
 				4BE77A2E1D84ADFB00BC3827 /* File.cpp in Sources */,
diff --git a/Storage/Disk/PCMPatchedTrack.cpp b/Storage/Disk/PCMPatchedTrack.cpp
new file mode 100644
index 000000000..97a9c35d4
--- /dev/null
+++ b/Storage/Disk/PCMPatchedTrack.cpp
@@ -0,0 +1,16 @@
+//
+//  PCMPatchedTrack.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 15/12/2016.
+//  Copyright © 2016 Thomas Harte. All rights reserved.
+//
+
+#include "PCMPatchedTrack.hpp"
+
+using namespace Storage::Disk;
+
+void PCMPatchedTrack::add_segment(const Time &start_position, const PCMSegment &segment)
+{
+	patches_.emplace_back(start_position, segment);
+}
diff --git a/Storage/Disk/PCMPatchedTrack.hpp b/Storage/Disk/PCMPatchedTrack.hpp
new file mode 100644
index 000000000..2a5d1bb62
--- /dev/null
+++ b/Storage/Disk/PCMPatchedTrack.hpp
@@ -0,0 +1,51 @@
+//
+//  PCMPatchedTrack.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 15/12/2016.
+//  Copyright © 2016 Thomas Harte. All rights reserved.
+//
+
+#ifndef PCMPatchedTrack_hpp
+#define PCMPatchedTrack_hpp
+
+#include "PCMTrack.hpp"
+
+namespace Storage {
+namespace Disk {
+
+/*!
+	A subclass of @c Track that patches an existing track with PCM segments.
+*/
+class PCMPatchedTrack: public Track {
+	public:
+		/*!
+			Constructs a @c PCMPatchedTrack that will return events from @c underlying_track in
+			regions where it has not had alternative PCM data installed.
+		*/
+		PCMPatchedTrack(const PCMTrack &underlying_track);
+
+		/*!
+			Replaces whatever is currently on the track from @c start_position to @c start_position + segment length
+			with the contents of @c segment.
+		*/
+		void add_segment(const Time &start_position, const PCMSegment &segment);
+
+		// To satisfy Storage::Disk::Track
+		Event get_next_event();
+		Time seek_to(Time time_since_index_hole);
+
+	private:
+		const PCMTrack &underlying_track_;
+		struct Patch {
+			Time start_position;
+			PCMSegment segment;
+			Patch(const Time &start_position, const PCMSegment &segment) : start_position(start_position), segment(segment) {}
+		};
+		std::vector<Patch> patches_;
+};
+
+}
+}
+
+#endif /* PCMPatchedTrack_hpp */