Karlfeldt vs Dickens vs Eliot - three learned men

In the poem Sång efter skördeanden the Swedish poet Erik Axel Karlfeldt, describes how Fridolin "talar med bönder på böndernas sätt men med lärde män på latin" - "speaks with peasants in peasants' ways but with learned men in Latin".

It is a very useful expression in Swedish. The problem is to find an equivalent English saying that describes the ability to change language and style according to whom you speak with.

The best thing I found so far is originally from Charles Dickens' Our Mutual Friend:

‘For I aint, you must know,’ said Betty, ‘much of a hand at reading writing-hand, though I can read my Bible and most print. And I do love a newspaper. You mightn’t think it, but Sloppy is a beautiful reader of a newspaper. He do the Police in different voices.’

The last sentence, He do the Police in different voices, was taken up by T. S. Eliot, who used it as the working title of The Waste Land.

Unfortunately, that phrase is a far cry from Karlfeldt's lines, at least for my purpose to describe someone who is able to adapt his language to the situation. If anyone has any better proposal, feel free to post it.