Given all of the following:
Sauron is/was a maiar of Aule the Smith
The Noldor Elves became more or less disciples of Aule the Smith.
The Valar and the Maiar have had far more concourse with the Elves than with Men, it would makes sense that they mostly spoke either their own langauge, or VQ.
The magic of Ea is tied up in Langauge and its intonation from the beginnings
It would make sense that when Sauron codified the Black Speech, that it basically was a derivative of Elvish.
That's a very interesting line of thought 馃槈
But Black Speech could only be sort of a derivative of Elvish if you can turn a language into its contrary, I I can say so 馃槈 The elven tongues (whichever you take) don't show much of a relation to what little you of Black Speech. Besides, I would guess (I don't know if it's stated anywhere) that the Black Speech would come from Morgoth rather than Sauron. That would make it a little strange for the Black Speech to be related to an elven language; one might rather guess then that, if at all, it would be related to Valarin, wouldn't it?
(I'm confusing myself^^'馃槈
Yeah it could be a twisted form of Valarin, a secret language spun by Morgoth known only by the few. This also ties in because Valarin, much like the Black Speech was not meant to be pleasing upon the ears of those Elves who heard it spoken. Even though it was a "Divine" language.
"When the Eldar arrived in Valinor, the Valar and the Maiar quickly adopted Quenya and sometimes even used it among themselves. Yet Valarin was by no means displaced by Quenya, and it could still be heard when the Valar were having their great debates. "The tongues and voices of the Valar are great and stern," R煤mil of Tirion wrote, "and yet also swift and subtle in movement, making sounds that we find hard to counterfeit; and their words are mostly long and rapid, like the glitter of swords, like the rush of leaves in a great wind or the fall of stones in the mountains." Pengolodh is less lyrical, and also less courteous: "Plainly the effect of Valarin upon Elvish ears was not pleasing." (WJ:398) Valarin employed many sounds that were alien to the Eldarin languages. "
Sourced from
http://www.uib.no/people/hnohf/valarin.htm
There are indeed Valarin and Eldarin elements in the Black speech, compare for example the words "Ring" (BS: 'nazg', V: ?'na拧k芒d'馃槈 and "orc" (BS: 'uruk', Q 'urco', S 'orc', primitive eldarin 'uruk'馃槈 in BS and V/E; the grammatical agglutinating structure reminds of Ad没naic which seems probable as well.
Gandalf was referring to the F毛anorian script when he said that, no?
Here's what HKF had to say about Orkish and the Black Speech....