What tone to use when opening

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 opening. 

Exordium (Opening speech) – What kind of tone to use in it

"The exordium (opening or introductory speech in a trial) ought to be spoken with a low and modest voice; for to begin in an unpresuming tone is not only agreeable to the auditors (ie the judge and jury)as it shows how great a respect you have for them, but is also an advantage to yourself; for you will thereby be able to manage your voice much better, and work it up by degrees of moderation, to a higher pitch of warmth and passion, which, not attended to, will cause you at first to be out of breath, for want of proper management, and perhaps you will not be able to recover yourself during the whole of your speech. This does not, however, mean that you should begin so low as to be heard by only a few people; but on the contrary, you ought to speak at first, so clear and distinct as to be heard without the least difficulty by every attentive listener. Some clergymen are very faulty in beginning their discourses so low, that hardly any person in the congregation can hear them; but, all of a sudden they raise their voices to such a height, that every body’s ears are offended and astonished.

The proper method is to speak the exordium in a soft and easy tone, and in a lower key, together with a more humble address, than the other parts of your speech.

But this rule admits of an exception; for there are some exordiums that do not fall under it, such as those that begin in an abrupt and unexpected manner. As that of Mr Fox, in the House of Commons, in February 1784, in answer to a declaration from Mr Pitt that his Majesty had not, in compliance with the resolutions of the House, dismissed his ministers:

“I have just heard the declaration of the right honourable gentleman with the greatest astonishment and concern. It was a language that House had never heard since the revolution, or at least since the accession of the present royal family. What was it but a fiat and peremptory negative to the sentiments and wishes of the House of Commons, who on their part had employed every caution and every delicacy? In what situation then was this branch of the legislature involved? To what degree of insignificance were the representatives of the people and the people themselves reduced?Could it be said that they had any longer the least influence in the constitution of the country? I will answer baldly, and to the point – in my opinion the matter is nearly at a crisis.”

So abrupt an opening speech as this is not very common, and seldom found but upon very extra-ordinary occasions. When, however, such a tone is used, it is evident that it is to be spoken with an elevated tone, according to the passion, either of anger that transports, or of grief that afflicts, and which obliges you to set out so abruptly in your discourse."