Elvish, as coming from the elves, can hardly be too bad, can it? Actually, the inscription of the ring *is* in Black Speech, but written in elven runes. Suppose the dark side was either not bright enough or too lazy to make up runes of their own^^'
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.
__________________ Among the tales of sorrow and of ruin that come down to us from the darkness of those days there are yet some in which amid weeping there is joy and under the shadow of death light that endures.
J.R.R. Tolkien, "Of Beren and Luthien" from the Silmarilion
That's a very interesting line of thought
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 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^^')
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," Rśmil 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. "
__________________ Yet the making of things is in my heart from my own making by thee; and the child of little understanding that makes a play of the deeds of his father may do so without without thought of mockery, but because he is the son of his father.
There are indeed Valarin and Eldarin elements in the Black speech, compare for example the words "Ring" (BS: 'nazg', V: ?'nakād') and "orc" (BS: 'uruk', Q 'urco', S 'orc', primitive eldarin 'uruk') in BS and V/E; the grammatical agglutinating structure reminds of Adūnaic which seems probable as well.
__________________ Life is complex: it has both real and imaginary components.