Volume 4, prepared by cello specialist Michael Corssen, is devoted almost exclusively to playing in positions. Positions 2, 3 and 4 are introduced and trained using familiar songs and delightful short recital pieces, some of them specially written for the volume by Bertold Hummel. Changes of position are first marked with a sign in the music so that they can be explicitly practiced. The volume provides varied suggestions for this purpose, encouraging learners to approach this technical challenge from different angles and to practice with imagination. The tutor is rounded off with an excursion into positions 5 and 6. Volume 4 also introduces the tenor clef and explains how to produce harmonics.