Romanian to English Art/Literary General / Conversation / Greetings / Letters Journalistic Article on conductor

This part of this journalistic music review about a famous conductor is talking about his performance and his effect on the audiences. I am not sure if I have the meaning correct here as I am not clear on the structure and use of "când" and "până". The context reads:

" XX posedă autoritatea, o autoritate când imperativă până la violență, când insinuantă și suplă.

I think it means:

"XX can be authoritative; an authority that becomes aggressive when required, and when suggestive, it is elegant."

However, this is a clumsy translation so I am not sure if I have fully understood the phrase.