One unique feature lets you touch any section of the orchestra to hear its instruments isolated from the rest of the orchestra. By default, this feature is available in Beethoven's 5th Symphony. To unlock it for the other seven selections requires a $0.99 in-app purchase.
I don't think I've seen any other app utilize the power of a computer in a better or more compelling way. The app is not a series of performances, but contains many insights into the selections, and the composers.
Having said that, I have a few nits to pick. Charging an additional $0.99 in an app that is already $14 seems very Scrooge-like. It should just be thrown in. The selections themselves are excerpts, not complete works. I realize complete symphonies would take a lot of space, and hearing a movement is just not the same as getting the whole performance. There are links to the iTunes Store to download the complete works.
This is the kind of app that should support Apple AirPlay so it can be seen on a big screen with better audio. Sadly, the app doesn't appear to fully support it. I could see an image of the orchestra on my Apple TV-powered display, but the music never started playing. It did work in mirror mode, but the aspect ratio isn't right. The audio is pretty good, and is in stereo if you listen on a headset or an external source. The iPad speaker is no way to experience this app.
The Orchestra is an extraordinary way to show off what a great app can do. Classical music lovers will enjoy this app very much.
This app is, not surprisingly, a big one. Almost 2 GB without the in-app purchase, and I had to do a bit of house cleaning to make it fit. This app requires iOS 6.0 or above, and works on the second-, third- and fourth-generation iPad, and iPad mini.