No, he isn't a castrato. They stopped doing that over a century ago, thank goodness. Modern countertenors use falsetto, whereas castrati used their natural voices, which simply hadn't developed, since they were castrated before their voices changed. Jaroussky has a very natural-sounding falsetto in the soprano range, which is quite rare. Most countertenors are in the alto or mezzo range. Beaufiul voice, superb musician.
---In FairfieldLife@yahoogroups.com, <jr_esq@...> wrote: He could be a castrato, which was practiced in Europe many years ago. But I heard one of these guys singing at the Notre Dame Cathedral mass in Paris a few years ago. It was a new experience for me at that time to hear a guy with such a high voice range (a counter tenor according to Wikipedia).