Piece of music from America on old piano (4)
I believe the answer is:
opus
'piece of music' is the definition.
('opus' can be a synonym of 'piece of music')
'america on old piano' is the wordplay.
'america' becomes 'us' (abbreviation for the United States).
'on' says to put letters next to each other.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'piano' becomes 'p'.
'o'+'p'='op'
'us' put after 'op' is 'OPUS'.
'from' acts as a link.
(Other definitions for opus that I've seen before include "Composition - magnum __" , "Work of 25 perhaps" , "Composer's catalogue number" , "Work (of a composer?)" , "Artistic work" .)