Conversation so far:
Where was Ai born?
Los Angeles.
When did she first show interest in music?
early teens.
what kind of music did she perform as a teenager?
gospel choir.
was she raised in a religious environment?
Methodist Episcopal Church of Los Angeles.
when did she change from gospel music to other kinds of music?
In 1999.

Question: what happened in 1999?
Self-contained rewrite: What happened in 1999 to cause Ai to change from gospel music to other kinds?