Music and painting are the most common chord phenomena, based on the physical and mathematical forms of chords, distributed as chord fields (quantum fields), respectively expressing time, space and their mirror relations, both of which are physical events and spiritual events. Strings are the spatial (geometric) semantics of chords, and chords are the characteristic spectrum of strings: different chords contain different spatial semantics: major triads = closed chords (contour lines), minor triads = open chords (facet lines), proportional sequence chords = membrane chords (non-linear space), the three types of strings form a spatial field (spatial language) and produce all spatial states and interactions. Painting is a chord space event, including the natural laws of space and physical and mathematical forms, and is also the observation basis and application field of string theory, which is the main content of this book.