diff --git a/docs/changelog.rst b/docs/changelog.rst
index 0ff362f8..f50ff426 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -41,6 +41,20 @@ v0.20.0 (UNRELEASED)
   make sense for a server such as Mopidy. Currently the only way to find out if
   it is in use and will be missed is to go ahead and remove it.
 
+**Models**
+
+- Hide empty collections from :func:`repr()` representations.
+
+- Field values are no longer stored on the model instance when the value
+  matches the default value for the field. This makes two models equal when
+  they have a field which in one case is implicitly set to the default value
+  and in the other case explicitly set to the default value, but with otherwise
+  equal fields. (Fixes: :issue:`837`)
+
+- Changed the default value of :attr:`mopidy.models.Album.num_tracks`,
+  :attr:`mopidy.models.Track.track_no`, and
+  :attr:`mopidy.models.Track.last_modified` from ``0`` to :class:`None`.
+
 
 v0.19.4 (2014-09-01)
 ====================
diff --git a/mopidy/models.py b/mopidy/models.py
index 42313922..bedf8ca5 100644
--- a/mopidy/models.py
+++ b/mopidy/models.py
@@ -18,6 +18,8 @@ class ImmutableObject(object):
                 raise TypeError(
                     '__init__() got an unexpected keyword argument "%s"' %
                     key)
+            if value == getattr(self, key):
+                continue  # Don't explicitly set default values
             self.__dict__[key] = value
 
     def __setattr__(self, name, value):
@@ -29,6 +31,8 @@ class ImmutableObject(object):
         kwarg_pairs = []
         for (key, value) in sorted(self.__dict__.items()):
             if isinstance(value, (frozenset, tuple)):
+                if not value:
+                    continue
                 value = list(value)
             kwarg_pairs.append('%s=%s' % (key, repr(value)))
         return '%(classname)s(%(kwargs)s)' % {
@@ -70,13 +74,11 @@ class ImmutableObject(object):
         for key in self.__dict__.keys():
             public_key = key.lstrip('_')
             value = values.pop(public_key, self.__dict__[key])
-            if value is not None:
-                data[public_key] = value
+            data[public_key] = value
         for key in values.keys():
             if hasattr(self, key):
                 value = values.pop(key)
-                if value is not None:
-                    data[key] = value
+                data[key] = value
         if values:
             raise TypeError(
                 'copy() got an unexpected keyword argument "%s"' % key)
@@ -239,7 +241,7 @@ class Album(ImmutableObject):
     :param artists: album artists
     :type artists: list of :class:`Artist`
     :param num_tracks: number of tracks in album
-    :type num_tracks: integer
+    :type num_tracks: integer or :class:`None` if unknown
     :param num_discs: number of discs in album
     :type num_discs: integer or :class:`None` if unknown
     :param date: album release date (YYYY or YYYY-MM-DD)
@@ -260,7 +262,7 @@ class Album(ImmutableObject):
     artists = frozenset()
 
     #: The number of tracks in the album. Read-only.
-    num_tracks = 0
+    num_tracks = None
 
     #: The number of discs in the album. Read-only.
     num_discs = None
@@ -300,7 +302,7 @@ class Track(ImmutableObject):
     :param genre: track genre
     :type genre: string
     :param track_no: track number in album
-    :type track_no: integer
+    :type track_no: integer or :class:`None` if unknown
     :param disc_no: disc number in album
     :type disc_no: integer or :class:`None` if unknown
     :param date: track release date (YYYY or YYYY-MM-DD)
@@ -314,7 +316,7 @@ class Track(ImmutableObject):
     :param musicbrainz_id: MusicBrainz ID
     :type musicbrainz_id: string
     :param last_modified: Represents last modification time
-    :type last_modified: integer
+    :type last_modified: integer or :class:`None` if unknown
     """
 
     #: The track URI. Read-only.
@@ -339,7 +341,7 @@ class Track(ImmutableObject):
     genre = None
 
     #: The track number in the album. Read-only.
-    track_no = 0
+    track_no = None
 
     #: The disc number in the album. Read-only.
     disc_no = None
@@ -362,7 +364,7 @@ class Track(ImmutableObject):
     #: Integer representing when the track was last modified, exact meaning
     #: depends on source of track. For local files this is the mtime, for other
     #: backends it could be a timestamp or simply a version counter.
-    last_modified = 0
+    last_modified = None
 
     def __init__(self, *args, **kwargs):
         get = lambda key: frozenset(kwargs.pop(key, None) or [])
diff --git a/mopidy/mpd/translator.py b/mopidy/mpd/translator.py
index 252725ee..f3264a46 100644
--- a/mopidy/mpd/translator.py
+++ b/mopidy/mpd/translator.py
@@ -44,11 +44,11 @@ def track_to_mpd_format(track, position=None):
     if track.date:
         result.append(('Date', track.date))
 
-    if track.album is not None and track.album.num_tracks != 0:
+    if track.album is not None and track.album.num_tracks is not None:
         result.append(('Track', '%d/%d' % (
-            track.track_no, track.album.num_tracks)))
+            track.track_no or 0, track.album.num_tracks)))
     else:
-        result.append(('Track', track.track_no))
+        result.append(('Track', track.track_no or 0))
     if position is not None and tlid is not None:
         result.append(('Pos', position))
         result.append(('Id', tlid))
diff --git a/tests/test_models.py b/tests/test_models.py
index 43343ce7..56d6c76b 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -171,8 +171,8 @@ class ArtistTest(unittest.TestCase):
 
     def test_serialize_falsy_values(self):
         self.assertDictEqual(
-            {'__model__': 'Artist', 'uri': '', 'name': None},
-            Artist(uri='', name=None).serialize())
+            {'__model__': 'Artist', 'uri': '', 'name': ''},
+            Artist(uri='', name='').serialize())
 
     def test_to_json_and_back(self):
         artist1 = Artist(uri='uri', name='name')
@@ -318,13 +318,12 @@ class AlbumTest(unittest.TestCase):
 
     def test_repr_without_artists(self):
         self.assertEquals(
-            "Album(artists=[], images=[], name=u'name', uri=u'uri')",
+            "Album(name=u'name', uri=u'uri')",
             repr(Album(uri='uri', name='name')))
 
     def test_repr_with_artists(self):
         self.assertEquals(
-            "Album(artists=[Artist(name=u'foo')], images=[], name=u'name', "
-            "uri=u'uri')",
+            "Album(artists=[Artist(name=u'foo')], name=u'name', uri=u'uri')",
             repr(Album(uri='uri', name='name', artists=[Artist(name='foo')])))
 
     def test_serialize_without_artists(self):
@@ -551,14 +550,12 @@ class TrackTest(unittest.TestCase):
 
     def test_repr_without_artists(self):
         self.assertEquals(
-            "Track(artists=[], composers=[], name=u'name', "
-            "performers=[], uri=u'uri')",
+            "Track(name=u'name', uri=u'uri')",
             repr(Track(uri='uri', name='name')))
 
     def test_repr_with_artists(self):
         self.assertEquals(
-            "Track(artists=[Artist(name=u'foo')], composers=[], name=u'name', "
-            "performers=[], uri=u'uri')",
+            "Track(artists=[Artist(name=u'foo')], name=u'name', uri=u'uri')",
             repr(Track(uri='uri', name='name', artists=[Artist(name='foo')])))
 
     def test_serialize_without_artists(self):
@@ -738,6 +735,18 @@ class TrackTest(unittest.TestCase):
         self.assertNotEqual(track1, track2)
         self.assertNotEqual(hash(track1), hash(track2))
 
+    def test_ignores_values_with_default_value_none(self):
+        track1 = Track(name='name1')
+        track2 = Track(name='name1', album=None)
+        self.assertEqual(track1, track2)
+        self.assertEqual(hash(track1), hash(track2))
+
+    def test_copy_can_reset_to_default_value(self):
+        track1 = Track(name='name1')
+        track2 = Track(name='name1', album=Album()).copy(album=None)
+        self.assertEqual(track1, track2)
+        self.assertEqual(hash(track1), hash(track2))
+
 
 class TlTrackTest(unittest.TestCase):
     def test_tlid(self):
@@ -773,8 +782,7 @@ class TlTrackTest(unittest.TestCase):
 
     def test_repr(self):
         self.assertEquals(
-            "TlTrack(tlid=123, track=Track(artists=[], composers=[], "
-            "performers=[], uri=u'uri'))",
+            "TlTrack(tlid=123, track=Track(uri=u'uri'))",
             repr(TlTrack(tlid=123, track=Track(uri='uri'))))
 
     def test_serialize(self):
@@ -903,13 +911,12 @@ class PlaylistTest(unittest.TestCase):
 
     def test_repr_without_tracks(self):
         self.assertEquals(
-            "Playlist(name=u'name', tracks=[], uri=u'uri')",
+            "Playlist(name=u'name', uri=u'uri')",
             repr(Playlist(uri='uri', name='name')))
 
     def test_repr_with_tracks(self):
         self.assertEquals(
-            "Playlist(name=u'name', tracks=[Track(artists=[], composers=[], "
-            "name=u'foo', performers=[])], uri=u'uri')",
+            "Playlist(name=u'name', tracks=[Track(name=u'foo')], uri=u'uri')",
             repr(Playlist(uri='uri', name='name', tracks=[Track(name='foo')])))
 
     def test_serialize_without_tracks(self):
@@ -1036,7 +1043,7 @@ class SearchResultTest(unittest.TestCase):
 
     def test_repr_without_results(self):
         self.assertEquals(
-            "SearchResult(albums=[], artists=[], tracks=[], uri=u'uri')",
+            "SearchResult(uri=u'uri')",
             repr(SearchResult(uri='uri')))
 
     def test_serialize_without_results(self):