jdsmodulus wrote: ...why not just play it how it it written?...
There's at least two ablums out of the "original versions" of songs the GD covered, and I don't hear the Grateful Dead "cover" a single one the way it was originally written, let alone in the same Key.
Musicians tend to make things they like "their own".
The DSO premise is basically the opposite of this. They would play it how it was written.