counter spell of the Balrog

[tinewelt]

Ah, upon rereading the reference, I find it only applies to the balrog of Moria, and possibly only in this one scene Out of interest, the reference is from the letters.
Letter 210

20. The Balrog never speaks or makes any vocal sound at all. Above all he does not laugh or sneer. .... Z may think that he knows more about Balrogs than I do, but he cannot expect me to agree with him.

So, even if this is a one time instance, how can it be explained if the Balrog does not speak? Gandalf specifically says counter-spell. I am lost! Any more references?