diff --git a/docs/installation/despotify.rst b/docs/installation/despotify.rst
index b6053b16..07a3cd9a 100644
--- a/docs/installation/despotify.rst
+++ b/docs/installation/despotify.rst
@@ -16,7 +16,7 @@ Installing despotify
 *Linux:* Install despotify's dependencies. At Debian/Ubuntu systems::
 
     sudo aptitude install libssl-dev zlib1g-dev libvorbis-dev \
-        libtool libncursesw5-dev libao-dev
+        libtool libncursesw5-dev libao-dev python-dev
 
 *OS X:* In OS X you need to have `XCode
 <http://developer.apple.com/tools/xcode/>`_ installed, and either `MacPorts
@@ -46,7 +46,6 @@ file so that it reads::
 *All OS:* Build and install despotify::
 
     cd despotify/src/
-    make
     sudo make install
 
 
@@ -59,7 +58,6 @@ Build and install spytify::
 
     cd despotify/src/bindings/python/
     export PKG_CONFIG_PATH=../../lib       # Needed on OS X
-    make
     sudo make install
 
 
diff --git a/docs/installation/gstreamer.rst b/docs/installation/gstreamer.rst
new file mode 100644
index 00000000..d8fc9029
--- /dev/null
+++ b/docs/installation/gstreamer.rst
@@ -0,0 +1,10 @@
+**********************
+Gstreamer installation
+**********************
+
+**TODO** Document Gstreamer installation on Linux, OS X and Windows.
+
+To install Gstreamer on OS X::
+
+    sudo port install py26-gst-python py26-gobject \
+        gstreamer-plugins-good gstreamer-plugins-ugly
diff --git a/docs/installation/index.rst b/docs/installation/index.rst
index bacefb77..d21b49ad 100644
--- a/docs/installation/index.rst
+++ b/docs/installation/index.rst
@@ -18,6 +18,7 @@ Dependencies
 
     despotify
     libspotify
+    gstreamer
 
 - Python >= 2.6
 - Dependencies for at least one Mopidy mixer:
@@ -36,18 +37,22 @@ Dependencies
 
     - see :doc:`despotify`
 
-  - LibspotifyBackend (Linux only)
+  - LibspotifyBackend (Linux, OS X and Windows)
 
     - see :doc:`libspotify`
 
+  - GstreamerBackend (Linux, OS X and Windows)
+
+    - see :doc:`gstreamer`
+
 
 Install latest release
 ======================
 
 To install the currently latest release of Mopidy using ``pip``::
 
-    sudo aptitude install python-pip                # On Ubuntu/Debian
-    sudo brew install pip                           # On OS X
+    sudo aptitude install python-setuptools python-pip   # On Ubuntu/Debian
+    sudo brew install pip                                # On OS X
     sudo pip install Mopidy
 
 To later upgrade to the latest release::
diff --git a/docs/installation/libspotify.rst b/docs/installation/libspotify.rst
index 3dfd8f5a..5d2448f7 100644
--- a/docs/installation/libspotify.rst
+++ b/docs/installation/libspotify.rst
@@ -12,6 +12,8 @@ To use the libspotify backend you must install libspotify and
     This backend requires a Spotify premium account, and it requires you to get
     an application key from Spotify before use.
 
+**TODO** Test and document installation on OS X.
+
 
 Installing libspotify
 =====================
diff --git a/mopidy/backends/__init__.py b/mopidy/backends/__init__.py
index e45dcf63..1a7e1559 100644
--- a/mopidy/backends/__init__.py
+++ b/mopidy/backends/__init__.py
@@ -104,7 +104,7 @@ class BaseCurrentPlaylistController(object):
         tracks = self.playlist.tracks
 
         assert at_position <= len(tracks), 'at_position can not be greater' \
-            + ' than  playlist length'
+            + ' than playlist length'
 
         if at_position is not None:
             tracks.insert(at_position, track)
@@ -337,6 +337,8 @@ class BasePlaybackController(object):
         self._state = self.STOPPED
         self._shuffled = []
         self._first_shuffle = True
+        self._play_time_accumulated = 0
+        self._play_time_started = None
 
     @property
     def next_track(self):
diff --git a/mopidy/backends/dummy.py b/mopidy/backends/dummy.py
index 0da24c44..b64cdfba 100644
--- a/mopidy/backends/dummy.py
+++ b/mopidy/backends/dummy.py
@@ -36,7 +36,7 @@ class DummyLibraryController(BaseLibraryController):
     find_exact = search
 
 class DummyPlaybackController(BasePlaybackController):
-    def _next(self):
+    def _next(self, track):
         return True
 
     def _pause(self):
@@ -45,7 +45,7 @@ class DummyPlaybackController(BasePlaybackController):
     def _play(self, track):
         return True
 
-    def _previous(self):
+    def _previous(self, track):
         return True
 
     def _resume(self):
diff --git a/mopidy/backends/libspotify.py b/mopidy/backends/libspotify.py
index edffa3af..48c11f4b 100644
--- a/mopidy/backends/libspotify.py
+++ b/mopidy/backends/libspotify.py
@@ -181,6 +181,7 @@ class LibspotifySessionManager(SpotifySessionManager, threading.Thread):
         self.core_queue = core_queue
         self.connected = threading.Event()
         self.audio = AlsaController()
+        self.session = None
 
     def run(self):
         self.connect()
@@ -219,9 +220,11 @@ class LibspotifySessionManager(SpotifySessionManager, threading.Thread):
         """Callback used by pyspotify"""
         logger.debug('Notify main thread')
 
-    def music_delivery(self, *args, **kwargs):
+    def music_delivery(self, session, frames, frame_size, num_frames,
+            sample_type, sample_rate, channels):
         """Callback used by pyspotify"""
-        self.audio.music_delivery(*args, **kwargs)
+        self.audio.music_delivery(session, frames, frame_size, num_frames,
+            sample_type, sample_rate, channels)
 
     def play_token_lost(self, session):
         """Callback used by pyspotify"""
diff --git a/mopidy/mixers/nad.py b/mopidy/mixers/nad.py
index d82a19a3..4aec79cd 100644
--- a/mopidy/mixers/nad.py
+++ b/mopidy/mixers/nad.py
@@ -80,6 +80,7 @@ class NadTalker(BaseProcess):
     def __init__(self, pipe=None):
         super(NadTalker, self).__init__()
         self.pipe = pipe
+        self._device = None
 
     def _run(self):
         self._open_connection()
diff --git a/mopidy/mpd/frontend.py b/mopidy/mpd/frontend.py
index 21d1752b..d7c21a31 100644
--- a/mopidy/mpd/frontend.py
+++ b/mopidy/mpd/frontend.py
@@ -53,6 +53,7 @@ class MpdFrontend(object):
     def __init__(self, backend=None):
         self.backend = backend
         self.command_list = False
+        self.command_list_ok = False
 
     def handle_request(self, request, add_ok=True):
         if self.command_list is not False and request != u'command_list_end':
@@ -286,7 +287,7 @@ class MpdFrontend(object):
             songpos = int(songpos)
             track = self.backend.current_playlist.playlist.tracks[songpos]
             self.backend.current_playlist.remove(track)
-        except IndexError as e:
+        except IndexError:
             raise MpdAckError(u'Position out of bounds')
 
     @handle_pattern(r'^deleteid "(?P<songid>\d+)"$')
diff --git a/mopidy/mpd/server.py b/mopidy/mpd/server.py
index e6abb633..bd37c998 100644
--- a/mopidy/mpd/server.py
+++ b/mopidy/mpd/server.py
@@ -67,15 +67,15 @@ class MpdSession(asynchat.async_chat):
     def found_terminator(self):
         data = ''.join(self.input_buffer).strip()
         self.input_buffer = []
-        input = data.decode(ENCODING)
-        logger.debug(u'Input: %s', indent(input))
-        self.handle_request(input)
+        request = data.decode(ENCODING)
+        logger.debug(u'Input: %s', indent(request))
+        self.handle_request(request)
 
-    def handle_request(self, input):
+    def handle_request(self, request):
         my_end, other_end = multiprocessing.Pipe()
         self.core_queue.put({
             'command': 'mpd_request',
-            'request': input,
+            'request': request,
             'reply_to': pickle_connection(other_end),
         })
         my_end.poll(None)
diff --git a/mopidy/process.py b/mopidy/process.py
index 9459f816..d3c1d03e 100644
--- a/mopidy/process.py
+++ b/mopidy/process.py
@@ -14,8 +14,8 @@ class BaseProcess(multiprocessing.Process):
         except KeyboardInterrupt:
             logger.info(u'Interrupted by user')
             sys.exit(0)
-        except SettingsError, e:
-            logger.error(e)
+        except SettingsError as e:
+            logger.error(e.message)
             sys.exit(1)
 
     def _run(self):
@@ -26,6 +26,8 @@ class CoreProcess(BaseProcess):
     def __init__(self, core_queue):
         super(CoreProcess, self).__init__()
         self.core_queue = core_queue
+        self._backend = None
+        self._frontend = None
 
     def _run(self):
         self._setup()