Jazz musician possibly bitter accepting work in oil company (8)

'jazz musician' is the definition.
Both the definition and answer are singular nouns.
Perhaps there's a link between them I don't understand?

'possibly bitter accepting work in oil company' is the wordplay.
'possibly bitter' becomes 'beer' (bitter is a type of beer).
'accepting' means one lot of letters goes inside another (inserted letters are accepted).
'work' becomes 'op' (abbreviation for opus).
'in' indicates putting letters inside.
'oil company' becomes 'BP' (British Petroleum).
'op' inserted within 'bp' is 'bopp'.
'beer' placed around 'bopp' is 'BEBOPPER'.

Can you help me to learn more?