diff --git a/beetsplug/duplicates.py b/beetsplug/duplicates.py
index 23b476d19..3a30773b1 100644
--- a/beetsplug/duplicates.py
+++ b/beetsplug/duplicates.py
@@ -14,15 +14,43 @@
 
 """List duplicate tracks or albums.
 """
+import shlex
 import logging
 
 from beets.plugins import BeetsPlugin
 from beets.ui import decargs, print_obj, vararg_callback, Subcommand
+from beets.util import command_output, displayable_path
 
 PLUGIN = 'duplicates'
 log = logging.getLogger('beets')
 
 
+def _checksum(item, prog):
+    """Run external `prog` on file path associated with `item`, cache
+    output as flexattr on a key that is the name of the program, and
+    return the key, checksum tuple.
+    """
+    args = shlex.split(prog.format(file=item.path))
+    key = args[0]
+    checksum = getattr(item, key, False)
+    if not checksum:
+        log.debug('%s: key %s on item %s not cached: computing checksum',
+                  PLUGIN, key, displayable_path(item.path))
+        try:
+            checksum = command_output(args)
+            setattr(item, key, checksum)
+            item.store()
+            log.info('%s: computed checksum for %s using %s',
+                     PLUGIN, item.title, key)
+        except Exception as e:
+            log.debug('%s: failed to checksum %s: %s',
+                      PLUGIN, displayable_path(item.path), e)
+    else:
+        log.debug('%s: key %s on item %s cached: not computing checksum',
+                  PLUGIN, key, displayable_path(item.path))
+    return key, checksum
+
+
 def _group_by(objs, keys):
     """Return a dictionary whose keys are arbitrary concatenations of attributes
     and whose values are lists of objects (Albums or Items) with those keys.
@@ -30,7 +58,7 @@ def _group_by(objs, keys):
     import collections
     counts = collections.defaultdict(list)
     for obj in objs:
-        key = '\001'.join(getattr(obj, k, obj.mb_albumid) for k in keys)
+        key = '\001'.join(getattr(obj, k, '') for k in keys)
         counts[key].append(obj)
     return counts
 
@@ -55,7 +83,9 @@ class DuplicatesPlugin(BeetsPlugin):
         self.config.add({'count': False})
         self.config.add({'album': False})
         self.config.add({'full': False})
+        self.config.add({'path': False})
         self.config.add({'keys': ['mb_trackid', 'mb_albumid']})
+        self.config.add({'checksum': 'ffmpeg -i {file} -f crc -'})
 
         self._command = Subcommand('duplicates',
                                    help=__doc__,
@@ -91,6 +121,11 @@ class DuplicatesPlugin(BeetsPlugin):
                                         callback=vararg_callback,
                                         help='report duplicates based on keys')
 
+        self._command.parser.add_option('-C', '--checksum', dest='checksum',
+                                        action='store',
+                                        help='report duplicates based on\
+                                        arbitrary command')
+
     def commands(self):
         def _dup(lib, opts, args):
             self.config.set_args(opts)
@@ -99,8 +134,10 @@ class DuplicatesPlugin(BeetsPlugin):
             album = self.config['album'].get()
             full = self.config['full'].get()
             keys = self.config['keys'].get()
+            checksum = self.config['checksum'].get()
 
             if album:
+                keys = ['mb_albumid']
                 items = lib.albums(decargs(args))
             else:
                 items = lib.items(decargs(args))
@@ -116,6 +153,11 @@ class DuplicatesPlugin(BeetsPlugin):
                     fmt = '$albumartist - $album - $title'
                 fmt += ': {0}'
 
+            if checksum:
+                for i in items:
+                    k, _ = _checksum(i, checksum)
+                keys = ['k']
+
             for obj_id, obj_count, objs in _duplicates(items,
                                                        keys=keys,
                                                        full=full):
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 4ba970a5f..f91f4d057 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -11,7 +11,9 @@ New features:
   ``callback=beets.ui.varargs_callback`` and a variable number of arguments.
 
 * :doc:`/plugins/duplicates`: The new ``keys`` option allows you to specify
-  arbitrary fields over which to consider potential duplicates.
+  arbitrary fields over which to consider potential duplicates. The new
+  ``checksum`` option allows the use of any arbitrary program to checksum
+  items as an alternative duplicate identification strategy.
 
 * :doc:`/plugins/lastgenre`: The new ``multiple`` option has been replaced
   with the ``count`` option, which lets you limit the number of genres added
diff --git a/docs/plugins/duplicates.rst b/docs/plugins/duplicates.rst
index 1aee141f7..1b0a5a35d 100644
--- a/docs/plugins/duplicates.rst
+++ b/docs/plugins/duplicates.rst
@@ -34,6 +34,7 @@ config file::
 	keys:
   	  - mb_trackid
 	  - album
+	checksum: 'ffmpeg -i {file} -f crc -'
 
 or on the command-line::
 
@@ -45,7 +46,12 @@ or on the command-line::
                           of tracks
     -F, --full            show all versions of duplicate
                           tracks or albums
-    -k KEYS, --keys=KEYS  report duplicates based on keys
+    -p, --path            print paths for matched items
+                          or albums
+    -k, --keys            report duplicates based on keys
+    -C CHECKSUM, --checksum=CHECKSUM
+                          report duplicates based on
+                          arbitrary command
 
 
 format
@@ -57,6 +63,11 @@ album. This uses the same template syntax as beets’ :doc:`path formats
 </reference/pathformat>`.  The usage is inspired by, and therefore
 similar to, the :ref:`list <list-cmd>` command.
 
+path
+~~~~
+
+Convenience wrapper for ``-f \$path``.
+
 count
 ~~~~~
 
@@ -80,13 +91,21 @@ has duplicates, not just the duplicates themselves.
 keys
 ~~~~
 
-The ``keys`` option (default: ``mb_trackid``) defines in which track
+The ``keys`` option (default: ``[mb_trackid, mb_albumid]``) defines in which track
 or album fields duplicates are to be searched. By default, the plugin
 uses the musicbrainz track and album IDs for this purpose. Using the
 ``keys`` option (as a YAML list in the configuration file, or as
 space-delimited strings in the command-line), you can extend this behavior
 to consider other attributes.
 
+checksum
+~~~~~~~~
+
+The ``checksum`` option (default: ``ffmpeg -i {file} -f crc -``) enables the use of
+any arbitrary command to compute a checksum of items. It overrides the ``keys``
+option the first time it is run; however, because it caches the resulting checksums
+as ``flexattrs`` in the database, you can use
+``--keys=name_of_the_checksumming_program any_other_keys`` the second time around.
 
 Examples
 --------
@@ -112,16 +131,20 @@ The same as the above but include the original album, and show the path::
 
   beet duplicates -acf '$path'
 
-
 Get tracks with the same title, artist, and album::
 
   beet duplicates -k title albumartist album
 
+Compute Adler CRC32 or MD5 checksums, storing them as flexattrs, and report back
+duplicates based on those values::
+
+  beet dup -C 'ffmpeg -i {file} -f crc -'
+  beet dup -C 'md5sum {file}'
+
 TODO
 ----
 
 - Allow deleting duplicates.
 - Provide option to invert key selection
-- Provide additional strategies for duplicate finding (fingerprint, hash, etc.)  
 
 .. _spark: https://github.com/holman/spark