diff --git a/OSBindings/Mac/Clock Signal/Info.plist b/OSBindings/Mac/Clock Signal/Info.plist
index c6ef0500a..20f8b00df 100644
--- a/OSBindings/Mac/Clock Signal/Info.plist	
+++ b/OSBindings/Mac/Clock Signal/Info.plist	
@@ -386,6 +386,8 @@
 			<string>Owner</string>
 			<key>LSTypeIsPackage</key>
 			<false/>
+			<key>NSDocumentClass</key>
+			<string>$(PRODUCT_MODULE_NAME).MachineDocument</string>
 		</dict>
 		<dict>
 			<key>CFBundleTypeExtensions</key>
@@ -406,6 +408,8 @@
 			<string>Owner</string>
 			<key>LSTypeIsPackage</key>
 			<false/>
+			<key>NSDocumentClass</key>
+			<string>$(PRODUCT_MODULE_NAME).MachineDocument</string>
 		</dict>
 		<dict>
 			<key>CFBundleTypeExtensions</key>
diff --git a/Storage/Disk/DiskImage/Formats/MSA.cpp b/Storage/Disk/DiskImage/Formats/MSA.cpp
index 9e24a87a3..ce7729290 100644
--- a/Storage/Disk/DiskImage/Formats/MSA.cpp
+++ b/Storage/Disk/DiskImage/Formats/MSA.cpp
@@ -8,16 +8,77 @@
 
 #include "MSA.hpp"
 
+#include "Utility/ImplicitSectors.hpp"
+
 using namespace Storage::Disk;
 
 MSA::MSA(const std::string &file_name) :
 	file_(file_name) {
+	const auto signature = file_.get16be();
+	if(signature != 0x0e0f) throw Error::InvalidFormat;
+
+	sectors_per_track_ = file_.get16be();
+	sides_ = 1 + file_.get16be();
+	starting_track_ = file_.get16be();
+	ending_track_ = file_.get16be();
+
+	// Create the uncompressed track list.
+	while(true) {
+		const auto data_length = file_.get16be();
+		if(file_.eof()) break;
+
+		if(data_length == sectors_per_track_ * 512) {
+			// This is an uncompressed track.
+			uncompressed_tracks_.push_back(file_.read(data_length));
+		} else {
+			// This is an RLE-compressed track.
+			std::vector<uint8_t> track;
+			track.reserve(sectors_per_track_ * 512);
+			uint16_t pointer = 0;
+			while(pointer < data_length) {
+				const auto byte = file_.get8();
+
+				// Compression scheme: if the byte E5 is encountered, an RLE run follows.
+				// An RLE run is encoded as the byte to repeat plus a 16-bit repeat count.
+				if(byte != 0xe5) {
+					track.push_back(byte);
+					++pointer;
+					continue;
+				}
+
+				pointer += 4;
+				if(pointer > data_length) break;
+
+				const auto value = file_.get8();
+				auto count = file_.get16be();
+				while(count--) {
+					track.push_back(value);
+				}
+			}
+
+			if(pointer != data_length || track.size() != sectors_per_track_ * 512) throw Error::InvalidFormat;
+			uncompressed_tracks_.push_back(std::move(track));
+		}
+	}
+
+	if(uncompressed_tracks_.size() != (ending_track_ - starting_track_ + 1)*sides_) throw Error::InvalidFormat;
 }
 
 std::shared_ptr<::Storage::Disk::Track> MSA::get_track_at_position(::Storage::Disk::Track::Address address) {
-	return nullptr;
+	if(address.head >= sides_) return nullptr;
+
+	const auto position = address.position.as_int();
+	if(position < starting_track_) return nullptr;
+	if(position >= ending_track_) return nullptr;
+
+	const auto &track = uncompressed_tracks_[size_t(position) * size_t(sides_) + size_t(address.head)];
+	return track_for_sectors(track.data(), sectors_per_track_, uint8_t(position), uint8_t(address.head), 0, 2, true);
 }
 
 HeadPosition MSA::get_maximum_head_position() {
-	return HeadPosition(10);
+	return HeadPosition(ending_track_);
+}
+
+int MSA::get_head_count() {
+	return sides_;
 }
diff --git a/Storage/Disk/DiskImage/Formats/MSA.hpp b/Storage/Disk/DiskImage/Formats/MSA.hpp
index 076f85201..5bd8542f0 100644
--- a/Storage/Disk/DiskImage/Formats/MSA.hpp
+++ b/Storage/Disk/DiskImage/Formats/MSA.hpp
@@ -12,6 +12,8 @@
 #include "../DiskImage.hpp"
 #include "../../../FileHolder.hpp"
 
+#include <vector>
+
 namespace Storage {
 namespace Disk {
 
@@ -25,10 +27,17 @@ class MSA final: public DiskImage {
 
 		// Implemented to satisfy @c DiskImage.
 		HeadPosition get_maximum_head_position() override;
+		int get_head_count() override;
 		std::shared_ptr<::Storage::Disk::Track> get_track_at_position(::Storage::Disk::Track::Address address) override;
 
 	private:
 		FileHolder file_;
+		uint16_t sectors_per_track_;
+		uint16_t sides_;
+		uint16_t starting_track_;
+		uint16_t ending_track_;
+
+		std::vector<std::vector<uint8_t>> uncompressed_tracks_;
 };
 
 
diff --git a/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.cpp b/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.cpp
index 1b3b6ae41..20851efa3 100644
--- a/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.cpp
+++ b/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.cpp
@@ -18,7 +18,7 @@
 
 using namespace Storage::Disk;
 
-std::shared_ptr<Track> Storage::Disk::track_for_sectors(uint8_t *const source, int number_of_sectors, uint8_t track, uint8_t side, uint8_t first_sector, uint8_t size, bool is_double_density) {
+std::shared_ptr<Track> Storage::Disk::track_for_sectors(const uint8_t *const source, int number_of_sectors, uint8_t track, uint8_t side, uint8_t first_sector, uint8_t size, bool is_double_density) {
 	std::vector<Storage::Encodings::MFM::Sector> sectors;
 
 	off_t byte_size = static_cast<off_t>(128 << size);
diff --git a/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.hpp b/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.hpp
index e656f24af..8db583ee6 100644
--- a/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.hpp
+++ b/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.hpp
@@ -16,8 +16,8 @@
 namespace Storage {
 namespace Disk {
 
-std::shared_ptr<Track> track_for_sectors(uint8_t *const source, int number_of_sectors, uint8_t track, uint8_t side, uint8_t first_sector, uint8_t size, bool is_double_density);
-void decode_sectors(Track &track, uint8_t *const destination, uint8_t first_sector, uint8_t last_sector, uint8_t sector_size, bool is_double_density);
+std::shared_ptr<Track> track_for_sectors(const uint8_t *source, int number_of_sectors, uint8_t track, uint8_t side, uint8_t first_sector, uint8_t size, bool is_double_density);
+void decode_sectors(Track &track, uint8_t *destination, uint8_t first_sector, uint8_t last_sector, uint8_t sector_size, bool is_double_density);
 
 }
 }