Machine that supplies more tightly packed boxes is quiet (9)

I believe the answer is:
dispenser
'machine that' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'more tightly packed boxes is quiet' is the wordplay.
'more tightly packed' becomes 'denser' (I've seen this in another clue).
'boxes' indicates putting letters inside (the outside letters must 'box' inside letters in).
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'is'+'p'='isp'
'denser' enclosing 'isp' is 'DISPENSER'.
'supplies' acts as a link.
Can you help me to learn more?
(Other definitions for dispenser that I've seen before include "Pharmacist" , "one to give out" , "One filling prescription" , "ATM" , "Chemist" .)
