44 Warm-Up and Performance Studies for Jazz, Pop and Gospel Choirs. Par GROGER BERTRAND. The 'Loop Songs' by Bertrand Gröger (Jazzchor Freiburg) are modern choral études for all SATB groups. Originally conceived as warm-ups or to break up the routine of repertoire rehearsals, many songs are also suitable as concert songs. The 44 compositions, divided into four levels of difficulty, allow for a var…