Jeanne Joulain was a student of Dupré, and has written several works for organ (as well as transcribed a number of Cochereau's improvisations). This is her short Prelude on "Hosanna Filio David"... it sounds to me very like a written-out improvisation - the first 4 notes of the theme are EVERYWHERE and sometimes simultaneously at normal speed and augmented. I've posted 2 other pieces by her HERE: http://www.contrebombarde.com/concerthall/music/631 as well as HERE: http://www.contrebombarde.com/concerthall/music/7484