Conversation so far:
What is Tristan and serialism and its connection with Olivier Messiaen?
Two years after Visions de l'Amen, Olivier Messiaen composed the song cycle Harawi, the first of three works inspired by the legend of Tristan and Isolde.
What was the Olivier Messiaen song cycle Harawi about?
Harawi is the first part of Messiaen's 'Tristan Trilogy', preceding the Turangalîla Symphony and the Cinq Rechants.
Was Olivier Messiaen commissioned to write any other songs besides Harawi?
Are there any other interesting aspect about Olivier Messiaen and his composing of Harawi?
Messiaen taught an analysis class at the Paris Conservatoire.
How long did Olivier Messiaen teach for?
After three years teaching analysis of twelve-tone scores, including works by Arnold Schoenberg, Messiaen experimented with ways of making scales of other elements analogous to the chromatic pitch scale.

Question: What else did he do in Budapest?
Self-contained rewrite: What else did Olivier Messiaen do in Budapest besides teach?