:up: Also, in a rather more formal context, a voice can be described as 'mellifluous' (which coincidentally, has a sort of association with butter - as it's derived from Latin words meaning 'flowing like honey'). ;-)
By the way, is it "in the mouth" or "on the tongue"?
Thanks so much, Bob.:up: I've looked up the word and that word describes perfectly well the voice I heard of a singer. (does this sentence sound strange by the way?...the voice I heard of a singer.)
I try to avoid using the expression for I and my Chinese taste-bud can't detect fake butter from real one, using it would present me as fraud. :-?
By the way, is it "in the mouth" or "on the tongue"? Either, though collocation is important: "melt", for example, collocates with 'mouth' - delicious food 'melts in the mouth'; if there's a word you just can't remember, however, it's 'on the tip of your tongue'.
there is an idiom which also uses the concept of butter,albeit melting in sb's mouth
(she looked as if butter wouldn't melt in her mouth)
meaning sb looks as if he/she would never do anything wrong, although you suspect they might
totally out of context,of course,but it favours the mouth and not the tongue.