Gloomy note written about world and its end? (6)

I believe the answer is:
morbid
'gloomy' is the definition.
(thesaurus)
'note written about world and its end?' is the wordplay.
I cannot really understand how this works, but
'note' could be 'd' (musical note) and 'd' is located in the answer.
'world' could be 'orb' (I have seen 'The World' mean 'orb' so perhaps 'world' could also mean 'orb') and 'orb' is present in the answer.
The remaining letters 'mi' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for morbid that I've seen before include "Displaying an unhealthy interest in unpleasant things" , "Of the mind, given to gloomy and unhealthy ideas" , "Inclined to dwell on unpleasant thoughts" , "Preoccupied with gloomy or unpleasant things" , "Sickly, unwholesome" .)
