The Opera Company of Brooklyn staged its “Magic Flute” over the weekend with a virtual orchestra instead of live musicians. How did it sound? “The Virtual Orchestra, developed by Realtime Music Solutions, which donated the hall and its services, behaved well. It allowed for pauses and shifts in tempo, thanks to the real-time control of an assistant at the synthesizer, and its surround loudspeakers (nearly 30 of them) created a sense of space. It sounded a little thin and tinny in the overture, but it never overpowered the singers and they appeared comfortable with their high-tech partner.”