Conversation so far:
What is one of the concertos he wrote?
Yi series, named for the I Ching (Yi Jing in pinyin).
Was this performed live anywhere?
CANNOTANSWER.
What was another piece that he wrote?
In 2008, Tan Dun was commissioned by Google and YouTube to write an inaugural symphony for the YouTube Symphony Orchestra (YTSO) project.
Are there any other interesting aspects about this article?
In April 2009, a mashup video of the submissions was premiered at Carnegie Hall, followed by a live performance of the work.
What was the title of the piece he wrote for Google and YouTube?
Eroica.
Does the article disclose how much they paid him for that?
CANNOTANSWER.
Does he write for specific instruments, like the piano for example?
the cello soloists.
When did he begin writing these pieces?
In the mid-1990s.
Is there another piece that he wrote mentioned in the article?
Originally titled Secret Land, Tan Dun wrote a concerto for twelve solo cellos and orchestra called Four Secret Road of Marco Polo .

Question: When did he write that?
Self-contained rewrite: When did Tan Dun write Secret Land?