How does improvisation, common to all three characters, also serve to turn the story in directions you did not expect?

Thomas reaches maturity as an artist when he learns to improvise. Bix Beiderbecke said, "One thing I like about jazz, kid, is that I don't know what's going to happen next. Do you?" Thomas is also able to start improvising with his life, and in the wake of war, to make braver and more unexpected choices. Song and Lin must do the same. How does this arc, common to all three characters, also serve to turn the story in directions you did not expect?

Improvisation or adaptability, ability to accept sudden changes served Song, Thomas and Lin well. They all seized opportunities as presented and matured. Thomas became an adept musician not tied to reading scores and came to the aid of the Shanghai Jews he knew. He also came to recognize he could not change individual's nature. Song balanced her love of China and embracement of the coming regime with her desire to nurture and save Thomas from certain persecution or death. Lin became a richer, fuller, more caring person.

I found the narrative intriguing. I had no idea what was going to happen. Their actions were unpredictable. I had no idea of the direction and was pleasantly surprised. Their improvisation was enthralling and very well done, definately added to the turbulent and chaotic time, created tension transporting the reader to time and place alongside the players.

It's true that there is a parallel in the novel between musical and narrative improvisation. The "narrative improvisation" is, basically, the author's skill in taking the story in unexpected directions. For while I thought that at the end Song and Thomas will be together, but the closer I got to the end the more obvious it became that they won't. Song's decision to go to the area where Communists were in control (rather than stay with Thomas in Shanghai) was unexpected (an improvisation, you might say) but after that I guessed that she will chose to follow her political instinct rather than her heart.

I think the biggest surprise in the story for me was that Song did not go with Thomas. Her actions with the boat tickets seemed like the height of improvisation - she didn't know what she was going to do until she did it - and in a moment completely changed both her life and Thomas's.