Tone of voice is pretty much everything in the business of voice-overs. I am often amazed at how many different voices and feelings I can express, simply with a shift in my tone. Even within one sentence, I can change my tone to offer my clients very different interpretations of their scripts.
When recording an audition, I (used to) record my name at the end of my audition. That is, I recorded the script sample and then, in the same tone of voice, I recorded my name which I then cut and paste to the beginning of the audition. That ensured that I’d say my name in the tone of voice that I wanted to express within my whole audition – upbeat and happy, sophisticated and professional, serious and austere, etc. This is not to say that I changed my voice, exactly, because consistency is also important. But, I simply adapted the tone to what is required for the script, capturing the listener’s ear and keeping their attention past the first two seconds. This was key since it only takes a few seconds for someone to decide that they are interested in your voice for audition purposes.
All that to say that the slightest change in tone can create a very different sound, feeling, and interpretation.
As for what sounds “right”, when listening back to my takes of a client’s script, I can just hear if it needs to be read again, read differently. With a straight face, my delivery might sound disengaged or boring, with a smile, my sound might be too phony; the perfect delivery is somewhat elusive in that it is difficult to put into words exactly how I know what sounds best. Through persistence and practice, I have simply learned to “hear” the subtle nuances my voice exudes.
I suppose that also answers the question for client’s everywhere… How do they know what they want in a voice talent? They know what they are looking for when they hear it!