Exploration time...
The Synthesizer V manual isn’t exactly exceptional, and it often leaves me wondering how one might use certain parameters in a practical setting. For example, why would I use “Tone Shift”?
Some time ago I learned that vowel sounds change as we lower or raise our voice. That is to say, vowels sound one way when we whisper, and another when we shout. This phenomenon is caused by a shift in emphasis of the harmonic frequencies of any given vowel.
For most pitched musical instruments, the fundamental frequency is the loudest partial, while the upper harmonics become progressively quieter. There are some exceptions, such as the oboe where the fifth harmonic (third overtone as oboes produce only odd harmonics) is the loudest. But the human vowel sounds are not so rigid.
“Don’t speak to me in that tone of voice!”
When you shout, the upper harmonics become emphasized. Whispering does the opposite.
In terms of singing, loud operatic singing emphasizes the upper harmonics, allowing the vocalist to be heard above an orchestra. (Remember, orchestral instruments become quieter in the upper harmonics, the opposite of a loud human voice.) Crooners, on the other hand, have stronger lower harmonics that sound like they are singing quietly into your ear. Or at least quietly into the microphone. (Note that microphone technology is crucial to the existence of crooning.)
Is this what the “Tone Shift” thing in SynthV is doing? Changing between an “outdoor” voice and an “indoor” voice? It kinda sounds like it, but I wanted to put my hypothesis to the test.
And here’s the result using the [a] vowel:
The red line represents a higher (not highest) “Tone Shift” setting, and the blue line represents a lower (not lowest) setting. Notice how the red fundamental is much quieter than the blue fundamental. Also note how the red upper harmonics are louder than the blue harmonics (except near the very top, which is getting to the limit of my hearing range.)
In practical terms, one could equate a higher “Tone Shift” setting to a louder voice, and/or one further from the microphone; and a lower setting to a quieter voice, and/or one closer to the microphone. Operatic versus crooning!
To be fair, however, the change is not super dramatic, but it’s enough to make a meaningful difference in the correct musical context.
Have fun!