Whatever might have been your intention when Riri wrote in January 1948, you did not enter the Conservatoire, but after the summer holiday you did begin attending Olivier Messiaen's classes there as a non-enrolled student. How this came about is unclear. Maybe Langlais recommended you to move on to his colleague. Possibly there was an awareness in the Beerblock circle of Messiaen's class, which for the past few years had been alive with revolutionary ideas about developing Arnold Schoenberg's serial method of composition, reinvigorating rhythm, exploring new tone colours and learning from the music of the world.

Messiaen, who was just short of forty when you joined his class, had returned to Paris seven years earlier, in the summer of 1941, from a prisoner-of-war camp in Silesia, and had been immediately invited by Claude Delvincourt, director of the Conservatoire, to teach a course in harmony. The routine teaching of harmony, though, was only part of his syllabus, for he was eager to communicate his wider enthusiasms, which went far beyond the academic curriculum of the Conservatoire. He began giving his students private lessons as well, at the home of Guy-Bernard Delapierre, a musician and Egyptologist he had met in the summer of 1940, when both of them had recently been captured by the invading Germans. In these private classes he analysed masterpieces of western music, from plainsong to works by living composers.