Recording new test case, listen in on evidence, firstly (8,4)

'recording' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I can't see?

'new test case listen in on evidence firstly' is the wordplay.
'new' indicates anagramming the letters.
'listen in' becomes 'tap' (tapping is a kind of listening in).
'on' is a charade indicator (letters next to each other).
'firstly' says to take the initial letters.
The initial letter of 'evidence' is 'e'.
'test'+'case'='testcase'
'testcase' is an anagram of 'cassette'.
'cassette'+'tap'+'e'='CASSETTE TAPE'

Can you help me to learn more?