Douze Etudes by Jacques Delécluse (born 1933) is a set of twelves studies often used as solos for exams or auditions. Written for intermediate to advanced level, they are considered quite difficult, the difficulty progressing throughout the book. Douze Etudes particularly helps to develop precision and mastery over the roll. It uses dynamic changes, placement of ornaments and frequent time changes. It is a must for serious percussionists and, as such, is widely used all over the world.