Of course the most difficult thing on the violin is always intonation. The second one is rhythm. If you play in tune, in time with a good sound that's already high level. Those three are the main things.

The other thing I knew I had was a high level of competitiveness.

The most difficult thing to do is drama.

Pitching is always a weird, difficult thing.

So, first you have to be able to play with a metronome. Then you take your freedom. If you play in an orchestra, you got to watch the conductor, he is like a metronome, but it is more difficult because he can change rhythms.

It is so tempting to try the most difficult thing possible.