This elementary teaching aims to convey the most important knowledge for jazz and pop musicians without unnecessary detours. The book is divided into three main parts: harmony theory, rhythm theory, and practical notation theory. All three areas are developed separately for better understanding but merge in musical practice. The reader can decide whether to start with harmony theory, rhythm theory, or notation, depending on their prior knowledge. The learning material is designed so that the book does not have to be worked through from front to back; rather, it is advisable to work on individual parts and immediately apply what has been learned in practice.