Marcel Bitsch (December 29, 1921, Toulouse – September 21, 2011, Paris) was a French composer, teacher and analyst. He studied at the Conservatoire de Paris and also was professor of counterpoint there. In his latter years he concentrated on teaching and analyzing the music of (mostly) J. S. Bach, producing analytic scores whose page layout was designed to convey the music's structural features. (reference: Wikipedia)
Bitsch's 20 Etudes for Trumpet, or Vingt Études pour Trompette if you speak French, are challenging unaccompanied technical exercises that are now a standard part of the conservatory repertoire. They may be used for auditions, and can be featured on a recital or jury exam.
Trumpeter David Baldwin has written extensively about the Bitsch Etudes, and an informative PDF is available on the Trumpet Guild website.
David Baldwin performing Etude #1
David Baldwin performing Etude #5