Conversation so far:
What is Tristan and serialism?
Messiaen composed the song cycle Harawi, the first of three works inspired by the legend of Tristan and Isolde.
What was the song about?
The second of these works about human (as opposed to divine) love was the result of a commission from Serge Koussevitzky.
Was he commissioned to write any other songs?
CANNOTANSWER.
Are there any other interesting aspects about this article?
Messiaen taught an analysis class at the Paris Conservatoire.
How long did he teach for?
In 1947 he taught (and performed with Loriod) for two weeks in Budapest.

Question: What else did he do in Budapest?
Self-contained rewrite: What else did Olivier Messiaen do in Budapest besides being a teacher in 1947?