anchor.diff:  program started are available to it. Then, assuming you have only one
   device sending MIDI clock, you can just execute:
   
  -code,clojure-----------------------------------------------------------------
  -code,clojure
  +[source,clojure]
  +----
   (show/sync-to-external-clock (afterglow.midi/sync-to-midi-clock))
  ------------------------------------------------------------------
  +----
   
   If there is ambiguity about which device’s MIDI clocks you want to
   process, Afterglow will complain. Resolve that by passing a substring
   which uniquely matches the name or description of the MIDI device that
   you want to sync to:
   
  -code,clojure------------------------------------------------
  -code,clojure
  +[source,clojure]
  +----
   (show/sync-to-external-clock
     (afterglow.midi/sync-to-midi-clock "traktor"))
  -------------------------------------------------
  +----
   
   From then on, as the BPM of that device changes, Afterglow will track it
   automatically. To check on the sync status, you can invoke:
   
  -code,clojure------------------------------------------------------------------
  -code,clojure
  +[source,clojure]
  +----
   (show/sync-status)
   ; -> {:type :midi, :status "Running, clock pulse buffer is full."}
  -------------------------------------------------------------------
  +----
   
   The calculated BPM of the synced show can be displayed like this:
   
  -code,clojure------------------------------------ code,clojure
  +[source,clojure]
  +----
   (metro-bpm (:metronome sample-show))
   ; -> 128.5046728971963
  -------------------------------------
  +----
   
   It will bounce up and down near the actual BPM as clock pulses are
   received, but overall track the beat quite well. To get a rock-solid
  
positive.code: 
  [source,clojure]
  ----
  code,clojure
  (show/add-effect! :color (global-color-cue
    (params/build-color-param :s 100 :l 50 :h :knob-1)))
  ----
  
negative.code: To shut down the syncing, just call `sync-to-external-clock` with no
  sync source:
  
  [source,clojure]
  ----
  (show/sync-to-external-clock)
  (show/sync-status)
  ; -> {:type :manual}
  ----
  
  == Syncing to Pro DJ Link
  
  If you are working with Pioneer club gear, such as the Nexus line of
  CDJs and mixers, you can use Pro DJ Link to sync much more precisely.
  