wwh,

I understand the point you're making. And you're absolutely correct with your example of not being able to affect pitch by increasing volume.

However, I think you're hyper-limiting the flexibility of our language with the 'loud pitch' example. A pitch can be loud or soft--and it can be performed in many different ways. All same pitches are not created equal as when a violinist plays a "D" on an open string v. playing that same "D" fingered elsewhere on the fingerboard. Professional violinists will argue over the relative merits of those identical "D's" (at least in terms of frequency) played open v. fingered till the end of time.

Now about Dickens and that loud pitch. Because a pitch can be performed at such a wide range of dynamic levels, Dickens is simply stating that the pitch of this particular character's voice had been pushed into its loudest level.

If Dickens had written that the character had used his voice at its highest pitch, we would imagine the sound of the character's voice sent to highest extremes, but we wouldn't have known whether the character's voice had been soft, medium or loud. But with the example you provide we simply are told that the pitch--whatever it was--was in its loudest dynamic range. "'Gentlemen,' said the mayor, at as loud a pitch as he could possibly force his voice to. The unknown quality is the pitch of the mayor's voice, but, whatever that pitch was--were he a monotonic mayor--it was his loudest in terms of dynamic level. I would suggest to Dickens, were he around, that the voice, although not usually singing, does have a wide range of pitches and that perhaps he could have written the phrase "'Gentlemen,' said the mayor, at as loud a range of pitches as he could possibly force his voice to..."

...but then that would have been rather wordy and cumbersome. Far be it from me to suggest to Dickens that he take on a few extra words.