In a later post, Michael has confirmed the spellings, so I have to conclude that both such beasts exist. But I'm confused.
The former I am familiar with, although I understand that the newly preferred (perhaps now legally required) terminology is simply "Asti". The term "spumante" is the style, which is heavily carbonated like Champagne. I can't recall whether it is made using the Méthode Champenoise process. It is made using one of the Muscat family of grapes. (The one we usually call muscat canelli in the USA but which I know goes by other names elsewhere.) I have never heard the term Moscato Spumante. I *am* familiar with Moscato d'Asti, which is made in the "frizzante" style (much less heavily carbonated) using the Charmat (bulk) process to induce carbonation. It is also made from the muscat canelli grape. Ian, Michael, or someone else please clear up my confusion. I am open to correction on any of the above statements.
I have heard this before and have never been sure whether it is a scientifically proven fact or an old wives' tale. Any comments, anyone?
Vino