Complex sentence: What makes Maniaci such an exciting singer is that he can sing these high castrato roles in a style and sound like the castrato of old, a sound the world hasn't heard for about a hundred and fifty years.
Split into simpler sentences: What makes Maniaci such an exciting as a singer is that he can sing these roles in a style and sound like the castrato. A sound the world hasn't heard for about a hundred and fifty years.