He can be low key when he desires; in the 1970's, he hosted a PBS show called American Enterprise
), which I believe was illustrating American industrial/technical innovation in the present (and he would announce he was portraying a character relevant to the subject), with references/dramas about the same in the nation's early years. He was to the point, but could be dramatic when required whether on camera, or narrating scenes talking about the early America's struggles.
Several months ago, someone on YouTube uploaded a couple of abridged episodes, but I wish the entire series was available somewhere. In my opinion, it was one of his best efforts in the lean years between TOS and TMP.