The following only applies when ``multiple`` is activated:

Return one valid genre even if its weight is lower then ```min_weight```.
Default for ```min_weight``` is now *10*.
Added new config option ```max_genres``` to limit the amount of genres returned.  Default is *3*.

beetsplug/lastgenre/__init__.py

@@ -61,20 +61,31 @@ def _tags_for(obj):
         return []
 
     tags = []
-    discarded_tags = []
-    min_weight = config['lastgenre']['min_weight'].get(int)
+    multiple = config['lastgenre']['multiple'].get(bool)
+    if multiple:
+        min_weight = config['lastgenre']['min_weight'].get(int)
+        max_genres = config['lastgenre']['max_genres'].get(int)
+    else:
+        min_weight = -1
+        max_genres = 1
+
     for el in res:
+        # pylast 0.5.x does not use Album.getTopTags, so we don't have a
+        # weight for album tags.  However:  Album.getInfo (they use that)
+        # returns only ~5 tags, so we use maximum weight for them
         if isinstance(el, pylast.TopItem):
-            if min_weight > -1:
-                if len(tags) > 0 and min_weight > int(el.weight):
-                    discarded_tags.append(el.item.get_name())
-                    continue
-            el = el.item
-        tags.append(el.get_name())
-    log.debug(u'last.fm tags: %s' % unicode(tags))
-    if min_weight > -1:
-        log.debug(u'last.fm tags (weight < {0}): {1}'.format(
-            min_weight, unicode(discarded_tags)))
+            weight = int(el.weight)
+            tag = el.item.get_name().lower()
+        else:
+            weight = 100
+            tag = el.get_name().lower()
+        if _is_allowed(tag):
+          if min_weight > -1 and min_weight > weight and len(tags) > 0:
+            return tags
+          log.debug(u'lastfm.tag (min. {}): {} [{}]'.format(min_weight, tag, weight))
+          tags.append(tag)
+          if len(tags) == max_genres:
+            return tags
     return tags
 
 def _is_allowed(genre):
@@ -83,24 +94,10 @@ def _is_allowed(genre):
     """
     if genre is None:
         return False
-    if genre.lower() in options['whitelist']:
+    if not options['whitelist'] or genre in options['whitelist']:
         return True
     return False
 
-def _find_allowed(genres):
-    """Given a list of candidate genres (strings), return an allowed
-    genre string. If `multiple` is on, then this may be a
-    comma-separated list; otherwise, it is one of the elements of
-    `genres`.
-    """
-    allowed_genres = [g.title() for g in genres if _is_allowed(g)]
-    if not allowed_genres:
-        return
-    if config['lastgenre']['multiple']:
-        return u', '.join(allowed_genres)
-    else:
-        return allowed_genres[0]
-
 def _strings_to_genre(tags):
     """Given a list of strings, return a genre. Returns the first string
     that is present in the genre whitelist (or the canonicalization
@@ -108,16 +105,16 @@ def _strings_to_genre(tags):
     """
     if not tags:
         return None
-    elif not options['whitelist']:
-        return tags[0].title()
 
     if options.get('c14n'):
         # Use the canonicalization tree.
-        for tag in tags:
-            return _find_allowed(find_parents(tag, options['branches']))
+        tags = find_parents(tags[0], options['branches'])
+
+    tags = [t.title() for t in tags]
+    if config['lastgenre']['multiple']:
+      return u', '.join(tags[:config['lastgenre']['max_genres'].get(int)])
     else:
-        # Just use the flat whitelist.
-        return _find_allowed(tags)
+      return tags[0]
 
 def fetch_genre(lastfm_obj):
     """Return the genre for a pylast entity or None if no suitable genre
@@ -214,7 +211,8 @@ class LastGenrePlugin(plugins.BeetsPlugin):
         self.config.add({
             'whitelist': os.path.join(os.path.dirname(__file__), 'genres.txt'),
             'multiple': False,
-            'min_weight': -1,
+            'min_weight': 10,
+            'max_genres': 3,
             'fallback': None,
             'canonical': None,
             'source': 'album',

docs/plugins/lastgenre.rst

@@ -86,22 +86,31 @@ Multiple Genres
 ---------------
 
 By default, the plugin chooses the most popular tag on Last.fm as a genre. If
-you prefer to use a list of *all available* genre tags, turn on the
-``multiple`` config option::
+you prefer to use a *list* of popular genre tags, turn on the ``multiple``
+config option::
 
     lastgenre:
         multiple: true
 
 Comma-separated lists of genres will then be used instead of single genres.
 
-If you want to filter out less popular tags, you can set the ``min_weight``
-config option::
+`Last.fm`_ provides a popularity factor aka *weight* for each *tag* ranging
+from 100 for the most popular *tag* down to 0 for the least popular *tags*.
+The plugin uses this *weight* to discard unpopular *tags*.  The default is to
+ignore *tags*, with a *weight* less then *10*. You can change this, by setting
+the ``min_weight`` config option::
 
     lastgenre:
-        min_weight: 50
+        min_weight: 15
 
-Only tags with a weight greater then ``min_weight`` will be used.  The weight
-ranges from 0 (unpopular) to 100 (most popular).
+However, if no tag with a *weight* greater then ``min_weight`` is found, the
+plugin uses the next best popular *tag*.
+
+By default, the pulgin uses a maxmimum of 3 genres.  You can change this by
+setting the ``max_genres`` config option::
+
+    lastgenre:
+        max_genres: 5
 
 
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