Yeah, I was wondering that too. How was he able to connect two wireless pro mics to the iPad and get it to output to the studio speakers? There must be extra hardware involved. If I bought the app, I'd be worried I couldn't do this.
The "magic" of this wasn't in pro mics, or having the right i/o gear - It was watching a whole performance come together live before our eyes, part layered upon part, the pieces coming together to make a satisfying "whole." It would have worked with one, lower-quaility mic, and if it was just the two of them sitting together on a living room sofa, no need for the fancy i/o gear at all. The pro gear was simply what was necessary to make it work at the quality level of national television. The studio audience can't respond if they can't hear what's going on; the band, 15 feet away, couldn't hear well enough to play its parts, and if the sound quality was lacking, it would have drawn our attention from the perfomers.
As much fun as it is to believe they got this right on the first take... hardly anyone is that good, and no musical performance goes unrehearsed on "live" TV. A few rehearsals a couple of hours before showtime doesn't make it any less magical. So what if the lyrics were up on the Teleprompter, so what if a really fine band was subtly backing them? They nailed it when the time came, in front of that live audience.
And knowing all that, it's still freakin' awesome, as far as I'm concerned.
Some of the happiest days of my career were spent in recording studios where, day after day, New York's top musicians, songwriters, and arrangers would gather to give their best for soft drinks, fast food, telecommunications companies, haircare products, home appliances... yeah, jingles. They'd run-down the lead sheets they found on their music stands a half-dozen times while the engineer pulled the sound together. Tape rolled, two or three takes later we were ready for a playback, and by Take 6 they usually had it nailed and were headed out the door to the next session. And as great as they all were (and still are), if they hadn't played together on a regular basis, if they didn't have the chops, things could not have come together that "easily."
Everybody's talkin' down the
thing that we've seen here
But it's still magic-making to me!