Syntax highlighting fails on copy-paste

[Deniz Dogan]

I've started writing my first "real" major mode, which I call 
guitar-mode. The code in its entirety can be viewed here: 
http://paste.lisp.org/display/121977

This is how I have implemented some basic syntax highlighting for chords 
 (@L78):

(defvar guitar-font-lock-keywords
  '((guitar-chord-matcher . ((1 'guitar-note-face)
                             (2 'guitar-chord-variation-face))))
  "Font lock keywords for guitar-mode.")

This works pretty well when _writing_ in a guitar-mode buffer but when I 
paste something from e.g. the web browser, not everything gets syntax 
highlighted until I edit the content around the chords.  The 
chords/lyrics I've tested this with are these: 
http://tabs.ultimate-guitar.com/r/red_hot_chili_peppers/under_the_bridge_crd.htm

So to summarize: when I copy-paste those chords/lyrics into a buffer 
with guitar-mode, not everything gets syntax highlighted until I edit 
the content around the chords.

Why is this?

Thanks,
Deniz Dogan