What tone to use in your narration

I have found it incredibly difficult to find books on how to deliver speeches if you are a barrister, and in fact was only able to find one, called "Hints for Public Speakers - aimed at young barristers and students of law" written by T Knox in 1797. The following quote is from this book, and covers the tone you should use when narrating the facts of your case. 

Narration (the statement of facts) – what tone necessary

It is not in the least necessary to raise your voice to any great vehemence, as many do, upon the proposition or narration (statement of facts) of your speech; for your business in this part of your speech is to inform your listeners, in order to make them properly understand the subject in question. It is therefore sufficient that your tone be a little higher than that in which you speak the exordium (introduction); only you must take care that your articulation be very clear and distinct, because the narration lays the groundwork of the whole speech, and therefore it is absolutely necessary that you should make it well heard, if you intend to raise your arguments upon that foundation. This is not the proper place for any vehemence of voice, which must be kept in reserve for the following parts of your speech.