I.
noun
VERB + HARP
▪ set , tune
▪
By means of pedals, a ~ can be set in any desired key.
II.
verb
PHRASAL VERB
harp on
ADVERB
▪ always , constantly
▪
He is always ~ing on about the war.
▪ still
PREPOSITION
▪ about
PHRASES
▪ keep ~ing on
▪
Don't keep ~ing on about my age!