Trumpet introducing bit of music – it makes a forceful entry (7)

I believe the answer is:
crowbar
'it makes a forceful entry' is the definition.
The definition suggests a singular noun which matches the answer.
'trumpet introducing bit of music' is the wordplay.
'trumpet' becomes 'crow' (I am not sure about this - if you are sure you should believe this answer much more).
'introducing' means one lot of letters go next to another (some letters go before others).
'bit of music' becomes 'bar' (I've seen this in another clue).
'crow'+'bar'='CROWBAR'
Can you help me to learn more?
(Other definitions for crowbar that I've seen before include "that can exert powerful leverage" , "Strong iron rod used as lever" , "Tool for breaking and entering" , "Iron rod with flattened end used as lever" , "Burglar's tool, perhaps" .)
