The subject of this study is the examination of aspects of musical intonation, here understood as the pitch allocation in music. The aim is to raise awareness of the possibilities, as well as the problems, that arise when dealing with intonation for musicians, sound engineers, and conductors. What possibilities does intonation offer regarding the quality of musical expression (expressive intonation)? What characteristics do melodic lines have, and what phenomena occur with simultaneously sounding tones? Why must a string instrument inevitably make compromises regarding intonation when playing together with a piano? This study initially addresses the fundamentals of auditory physiology and engages with the theory of intervals, consonances, and diatonic tonal systems.