I was fascinated watching a filmed rehearsal of Schumann's 4th Symphony with Herbert von Karajan conducting as he is my favorite symphony conductor. Anyone who has taken instruction from me in the Action/ReAction technique will recognize von Karajan's approach to the details of performing with special attention paid to the duration of notes and the fluid blending of one passage with the next to bring about a seemingly improvised yet thoroughly thought out delivery. I especially enjoyed seeing how much better the music became after his instructions on how a series of notes should be played. These are professional, top-level musicians who were made even better by a few words from the master.
My approach is to tell actors to think of themselves as singer/dancers as the rules governing these disciplines apply equally to acting. One can see how von Karajan's instructions regarding the playing of notes can be applied to the speaking of dialogue. Those who understand and use this are a delight to watch whether on the stage or the big screen.
There are seven parts to this series on YouTube and I watched them all only to wish there was more.