also: くちざみせん
noun
humming a shamisen tune; vocal imitation of shamisen
Refers to imitating the sound of a shamisen with one's mouth, often in a lively or rhythmic way. Can be used literally or figuratively.
彼は口三味線で祭りの曲を真似た。
He imitated a festival tune by humming it like a shamisen.
Figurative use: describing someone's speech as being as smooth and pleasing as a shamisen melody, often with a nuance of insincere or manipulative charm.
彼の口三味線に乗せられて、つい契約してしまった。
I was taken in by his smooth talk and ended up signing the contract.