By getting the key right on the piano (3)

Here is my best explanation:

'by' is the definition.
(thesaurus)

'the key right on the piano' is the wordplay.
'the key' becomes 'e' (I've seen this in other clues**).
'right' becomes 'r' (common abbreviation).
'on' is a charade indicator (letters next to each other).
'the piano' becomes 'p'.
'e'+'r'='er'
'er' put after 'p' is 'PER'.

'getting' is the link.