diff --git a/docs/_static/.placeholder b/docs/_static/.placeholder
deleted file mode 100644
index e69de29b..00000000
diff --git a/docs/_static/thread_communication.png b/docs/_static/thread_communication.png
new file mode 100644
index 00000000..4741a18c
Binary files /dev/null and b/docs/_static/thread_communication.png differ
diff --git a/docs/_static/thread_communication.txt b/docs/_static/thread_communication.txt
new file mode 100644
index 00000000..4357023f
--- /dev/null
+++ b/docs/_static/thread_communication.txt
@@ -0,0 +1,32 @@
+Script for use with www.websequencediagrams.com
+===============================================
+
+Main -> NadMixer: start
+activate NadMixer
+note over NadMixer: calibrate device
+NadMixer -> Main: ready
+Main -> MpdHandler/Backend: start
+activate MpdHandler/Backend
+MpdHandler/Backend -> despotify: connect to Spotify
+activate despotify
+MpdHandler/Backend -> Main: ready
+Main -> MpdServer/MpdSession: start
+activate MpdServer/MpdSession
+note over MpdServer/MpdSession: opens port
+MpdServer/MpdSession -> Main: ready
+Client -> MpdServer/MpdSession: connect
+Client -> MpdServer/MpdSession: play 1
+MpdServer/MpdSession -> MpdHandler/Backend: play 1
+MpdHandler/Backend -> despotify: play first track
+Client -> MpdServer/MpdSession: setvol 50
+MpdServer/MpdSession -> MpdHandler/Backend: setvol 50
+MpdHandler/Backend -> NadMixer: volume = 50
+Client -> MpdServer/MpdSession: status
+MpdServer/MpdSession -> MpdHandler/Backend: status
+MpdHandler/Backend -> NadMixer: volume?
+NadMixer -> MpdHandler/Backend: volume = 50
+MpdHandler/Backend -> MpdServer/MpdSession: status response
+MpdServer/MpdSession -> Client: status response
+despotify -> MpdHandler/Backend: end of track callback
+MpdHandler/Backend -> despotify: play second track
+MpdServer/MpdSession -> MpdHandler/Backend: stop
diff --git a/docs/development/internals.rst b/docs/development/internals.rst
index 10a79152..0062f2df 100644
--- a/docs/development/internals.rst
+++ b/docs/development/internals.rst
@@ -31,3 +31,13 @@ not Mopidy.
     "spytify" -> "despotify" [ label="use C library" ]
     "DespotifyBackend" -> "AlsaMixer" [ label="use mixer API" ]
     "AlsaMixer" -> "alsaaudio" [ label="use Python library" ]
+
+
+Thread communication
+====================
+
+.. warning::
+
+    This is a plan, and does not necessarily reflect what has been implemented.
+
+.. image:: /_static/thread_communication.png