A tricky piece this one, it was a proper devil in the original key of A, in C#/Db it's a right b*gger. Not a problem though as we have a proper musician to show us how it's done ...

But why?
Who is this "proper musician"?
What is their instrument?
And why did they transpose it into that key?
I'm sure that there are lots of tunes/pieces which could be made more difficult by transposing them into odd keys, but what's the point? It's not a way I'd normally want to spend
my weekend.
P.S. I don't really think it's any more difficult than in the original key of A, except for the fact that "nobody" practices the key of Db. On the English, that key (5 flats) also has a simple, consistent pattern, but it's a different pattern from the "more common" keys (up to 3 flats or 4 sharps), and probably very few players are used to it.