diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index f9cce8d2..08e7548f 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -6,7 +6,7 @@ jobs:
     strategy:
       matrix:
         platform: [ubuntu-latest]
-        python-version: [2.7, 3.5, 3.6, 3.7, 3.8]
+        python-version: [2.7, 3.5, 3.6, 3.7, 3.8, 3.9-dev]
 
     env:
       PY_COLORS: 1
@@ -82,4 +82,4 @@ jobs:
           python -m pip install tox sphinx
 
       - name: Lint with flake8
-        run: tox -e py-lint
\ No newline at end of file
+        run: tox -e py-lint
diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index 6c024e3d..dc861771 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -247,7 +247,7 @@ guidelines to follow:
    with the ``logging`` module, feed it through this function.
 
 Editor Settings
-^^^^^^^^^^^^^^^
+---------------
 
 Personally, I work on beets with `vim <http://www.vim.org/>`__. Here are
 some ``.vimrc`` lines that might help with PEP 8-compliant Python
@@ -285,6 +285,11 @@ Other ways to run the tests:
 
 You can also see the latest test results on `Linux`_ and on `Windows`_.
 
+Note, if you are on Windows and are seeing errors running tox, it may be related to `this issue`_,
+in which case you may have to install tox v3.8.3 e.g. ``python -m pip install tox=3.8.3``
+
+.. _this issue: https://github.com/tox-dev/tox/issues/1550
+
 Coverage
 ^^^^^^^^
 
diff --git a/beets/config_default.yaml b/beets/config_default.yaml
index 0fd6eb59..c75778b8 100644
--- a/beets/config_default.yaml
+++ b/beets/config_default.yaml
@@ -44,6 +44,7 @@ replace:
     '^\s+': ''
     '^-': _
 path_sep_replace: _
+drive_sep_replace: _
 asciify_paths: false
 art_filename: cover
 max_filename_length: 0
diff --git a/beets/dbcore/db.py b/beets/dbcore/db.py
index b13f2638..46b47a2e 100755
--- a/beets/dbcore/db.py
+++ b/beets/dbcore/db.py
@@ -19,6 +19,7 @@ from __future__ import division, absolute_import, print_function
 
 import time
 import os
+import re
 from collections import defaultdict
 import threading
 import sqlite3
@@ -84,6 +85,11 @@ class FormattedMapping(Mapping):
 
         if self.for_path:
             sep_repl = beets.config['path_sep_replace'].as_str()
+            sep_drive = beets.config['drive_sep_replace'].as_str()
+
+            if re.match(r'^\w:', value):
+                value = re.sub(r'(?<=^\w):', sep_drive, value)
+
             for sep in (os.path.sep, os.path.altsep):
                 if sep:
                     value = value.replace(sep, sep_repl)
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 0f41c38e..64e6ab85 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -235,6 +235,9 @@ Fixes:
 * :doc:`/plugins/ipfs`: Fix Python 3 compatibility.
   Thanks to :user:`musoke`.
   :bug:`2554`
+* Fix a bug that caused metadata starting with something resembling a drive
+  letter to be incorrectly split into an extra directory after the colon.
+  :bug:`3685`
 
 For plugin developers:
 

diff --git a/.github/workflows/integration_test.yaml b/.github/workflows/integration_test.yaml
index 05623bf2..1e8b3a77 100644
--- a/.github/workflows/integration_test.yaml
+++ b/.github/workflows/integration_test.yaml
@@ -12,10 +12,10 @@ jobs:
     steps:
       - uses: actions/checkout@v2
 
-      - name: Set up Python 3.8
+      - name: Set up latest Python version
         uses: actions/setup-python@v2
         with:
-          python-version: 3.8
+          python-version: 3.9-dev
 
       - name: Install base dependencies
         run: |
diff --git a/test/test_files.py b/test/test_files.py
index f3177967..13a8b440 100644
--- a/test/test_files.py
+++ b/test/test_files.py
@@ -102,6 +102,25 @@ class MoveTest(_common.TestCase):
         self.i.move()
         self.assertEqual(self.i.path, old_path)
 
+    def test_move_file_with_colon(self):
+        self.i.artist = u'C:DOS'
+        self.i.move()
+        self.assertIn('C_DOS', self.i.path.decode())
+
+    def test_move_file_with_multiple_colons(self):
+        print(beets.config['replace'])
+        self.i.artist = u'COM:DOS'
+        self.i.move()
+        self.assertIn('COM_DOS', self.i.path.decode())
+
+    def test_move_file_with_colon_alt_separator(self):
+        old = beets.config['drive_sep_replace']
+        beets.config["drive_sep_replace"] = '0'
+        self.i.artist = u'C:DOS'
+        self.i.move()
+        self.assertIn('C0DOS', self.i.path.decode())
+        beets.config["drive_sep_replace"] = old
+
     def test_read_only_file_copied_writable(self):
         # Make the source file read-only.
         os.chmod(self.path, 0o444)

Sanitize colons in drive-letter-like positions in Windows filenames like path separators
I have an album containing an artist named "F:A.R.". When doing any activity that involves moving this artist, the file is not moved to "M:\F:A.R." (I'm using unicode replacements instead of underscores), but to "M:\F:\A.R.".

### Problem

Running this command in verbose (`-vv`) mode:

```sh
~ ❯ beet -vv move "artist::^F.A.R"
user configuration: C:\Users\Gunther Schmidl\AppData\Roaming\beets\config.yaml
data directory: C:\Users\Gunther Schmidl\AppData\Roaming\beets
plugin paths:
Sending event: pluginload
lyrics: Disabling google source: no API key configured.
library database: M:\lib.db
library directory: M:\
Sending event: library_opened
Moving 1 item.
moving: M:\F꞉A․R․ ／ Muslimgauze\[1990] Manipulation (Live Extracts) ／ Death of Saint Jarnaii Singh Bhindranwaie\01-01 - Manipulation (Live Extracts).mp3
Sending event: before_item_moved
Sending event: item_moved
Sending event: database_change
Sending event: database_change
Sending event: cli_exit
```

Led to this problem:

Here's what it looks like in the database: https://i.imgur.com/Z5lvGqE.png

Here's a link to the music files that trigger the bug (if relevant):

https://www.dropbox.com/s/pastihu349z6kce/01-01%20-%20Manipulation%20%28Live%20Extracts%29.mp3?dl=0

### Setup

* OS: Windows 10 v2004
* Python version: 3.8.0
* beets version: latest trunk, but also happens in latest released version
* Turning off plugins made problem go away (yes/no): no

My configuration (output of `beet config`) is:

```yaml
lyrics:
    bing_lang_from: []
    auto: yes
    bing_client_secret: REDACTED
    bing_lang_to:
    google_API_key: REDACTED
    google_engine_ID: REDACTED
    genius_api_key: REDACTED
    fallback:
    force: no
    local: no
    sources:
    - google
    - lyricwiki
    - musixmatch
    - genius
directory: M:/
library: M:/lib.db

paths:
    default: $albumartist/[$year] $album%aunique{}/$disc-$track - $title
    singleton: Non-Album/$artist/$title
    comp: Compilations/[$year] $album%aunique{}/$disc-$track - $title

plugins: web mbsync discogs chroma lastgenre duplicates lyrics
lastgenre:
    source: artist
    force: no
    whitelist: yes
    min_weight: 10
    count: 1
    fallback:
    canonical: no
    auto: yes
    separator: ', '
    prefer_specific: no

replace:
    \\: "\uFF3C"
    /: "\uFF0F"
    \.{3}: "\u2026"
    \.: "\u2024"
    '[\x00-\x1f]': ''
    <: "\uFE64"
    '>': "\uFE65"
    ':': "\uA789"
    '"': "\uFF02"
    \?: "\uFF1F"
    \*: "\u204E"
    \|: "\u2502"
    \s+$: ''
    ^\s+: ''
    ^-: "\u2012"
path_sep_replace: "\uFF0F"
discogs:
    apikey: REDACTED
    apisecret: REDACTED
    tokenfile: discogs_token.json
    source_weight: 0.5
    user_token: REDACTED
    separator: ', '
    index_tracks: no
web:
    host: 127.0.0.1
    port: 8337
    cors: ''
    cors_supports_credentials: no
    reverse_proxy: no
    include_paths: no
duplicates:
    album: no
    checksum: ''
    copy: ''
    count: no
    delete: no
    format: ''
    full: no
    keys: []
    merge: no
    move: ''
    path: no
    tiebreak: {}
    strict: no
    tag: ''
chroma:
    auto: yes
```

test/test_files.py::MoveTest::test_move_file_with_colon_alt_separator
test/test_files.py::MoveTest::test_copy_already_at_destination test/test_files.py::MoveTest::test_copy_arrives test/test_files.py::MoveTest::test_copy_does_not_depart test/test_files.py::MoveTest::test_hardlink_arrives test/test_files.py::MoveTest::test_hardlink_changes_path test/test_files.py::MoveTest::test_hardlink_does_not_depart test/test_files.py::MoveTest::test_link_arrives test/test_files.py::MoveTest::test_link_changes_path test/test_files.py::MoveTest::test_link_does_not_depart test/test_files.py::MoveTest::test_move_already_at_destination test/test_files.py::MoveTest::test_move_arrives test/test_files.py::MoveTest::test_move_avoids_collision_with_existing_file test/test_files.py::MoveTest::test_move_changes_path test/test_files.py::MoveTest::test_move_departs test/test_files.py::MoveTest::test_move_file_with_colon test/test_files.py::MoveTest::test_move_file_with_multiple_colons test/test_files.py::MoveTest::test_move_in_lib_prunes_empty_dir test/test_files.py::MoveTest::test_move_to_custom_dir test/test_files.py::MoveTest::test_read_only_file_copied_writable test/test_files.py::HelperTest::test_ancestry_works_on_dir test/test_files.py::HelperTest::test_ancestry_works_on_file test/test_files.py::HelperTest::test_ancestry_works_on_relative test/test_files.py::HelperTest::test_components_works_on_dir test/test_files.py::HelperTest::test_components_works_on_file test/test_files.py::HelperTest::test_components_works_on_relative test/test_files.py::HelperTest::test_forward_slash test/test_files.py::AlbumFileTest::test_albuminfo_move_changes_paths test/test_files.py::AlbumFileTest::test_albuminfo_move_copies_file test/test_files.py::AlbumFileTest::test_albuminfo_move_moves_file test/test_files.py::AlbumFileTest::test_albuminfo_move_to_custom_dir test/test_files.py::ArtFileTest::test_art_deleted_when_items_deleted test/test_files.py::ArtFileTest::test_art_moves_with_album test/test_files.py::ArtFileTest::test_art_moves_with_album_to_custom_dir test/test_files.py::ArtFileTest::test_move_last_file_moves_albumart test/test_files.py::ArtFileTest::test_move_not_last_file_does_not_move_albumart test/test_files.py::ArtFileTest::test_setart_copies_image test/test_files.py::ArtFileTest::test_setart_sets_permissions test/test_files.py::ArtFileTest::test_setart_to_conflicting_file_gets_new_path test/test_files.py::ArtFileTest::test_setart_to_existing_art_works test/test_files.py::ArtFileTest::test_setart_to_existing_but_unset_art_works test/test_files.py::RemoveTest::test_removing_item_outside_of_library_deletes_nothing test/test_files.py::RemoveTest::test_removing_last_item_in_album_with_albumart_prunes_dir test/test_files.py::RemoveTest::test_removing_last_item_preserves_library_dir test/test_files.py::RemoveTest::test_removing_last_item_preserves_nonempty_dir test/test_files.py::RemoveTest::test_removing_last_item_prunes_dir_with_blacklisted_file test/test_files.py::RemoveTest::test_removing_last_item_prunes_empty_dir test/test_files.py::RemoveTest::test_removing_without_delete_leaves_file test/test_files.py::SoftRemoveTest::test_soft_remove_deletes_file test/test_files.py::SoftRemoveTest::test_soft_remove_silent_on_no_file test/test_files.py::SafeMoveCopyTest::test_self_copy test/test_files.py::SafeMoveCopyTest::test_self_move test/test_files.py::SafeMoveCopyTest::test_successful_copy test/test_files.py::SafeMoveCopyTest::test_successful_move test/test_files.py::SafeMoveCopyTest::test_unsuccessful_copy test/test_files.py::SafeMoveCopyTest::test_unsuccessful_move test/test_files.py::PruneTest::test_prune_existent_directory test/test_files.py::PruneTest::test_prune_nonexistent_directory test/test_files.py::WalkTest::test_ignore_directory test/test_files.py::WalkTest::test_ignore_everything test/test_files.py::WalkTest::test_ignore_file test/test_files.py::WalkTest::test_sorted_files test/test_files.py::UniquePathTest::test_conflicting_file_appends_1 test/test_files.py::UniquePathTest::test_conflicting_file_appends_higher_number test/test_files.py::UniquePathTest::test_conflicting_file_with_number_increases_number test/test_files.py::UniquePathTest::test_new_file_unchanged test/test_files.py::MkDirAllTest::test_child_does_not_exist test/test_files.py::MkDirAllTest::test_parent_exists