Music can be analysed by considering a variety of its elements, or parts (aspects, characteristics, features), individually or together. A commonly used list of the main elements includes pitch, timbre, texture, volume, duration, and form. The elements of music may be compared to the elements of art or design. Selection of elements According to Howard, there is little dispute about the principal constituent elements of music, though experts differ on their precise definitions. Harold Owen bases his list on the qualities of sound: pitch, timbre, intensity, and duration while John Castellini excludes duration. Gordon C. Bruner II follows the line of temporal-based deductions in association with musical composition, denoting music's primary components as "time, pitch, and texture." Most definitions of music include a reference to sound and sound perception can be divided into six cognitive processes. They are: pitch, duration, loudness, timbre, sonic texture and spatial location. A 'parameter' is any element that can be manipulated (composed) separately from other elements or focused on separately in an educational context. Leonard B. Meyer compares distinguishing parameters within a culture by their different constraints to distinguishing independent parameters within music, such as melody, harmony, timbre, "etc." The first person to apply the term parameter to music may have been Joseph Schillinger, though its relative popularity may be due to Werner Meyer-Eppler. Gradation is gradual change within one parameter, or an overlapping of two blocks of sound. Meyer lists melody, rhythm, timbre, harmony, "and the like" as principal elements of music, while Narmour lists melody, harmony, rhythm, dynamics, tessitura, timbre, tempo, meter, texture, "and perhaps others". According to McClellan, two things should be considered, the quality or state of an element and its change over time. Alan P. Merriam proposed a theoretical research model that assumes three aspects are always present in musical activity: concept, behaviour, and sound. Virgil Thomson lists the "raw materials" of music in order of their supposed discovery: rhythm, melody, and harmony; including counterpoint and orchestration. Near the end of the twentieth century music scholarship began to give more attention to social and physical elements of music. For example: performance, social, gender, dance, and theatre. Definition of music Does the definition of music determine its aspects, or does the combination of certain aspects determine the definition of music? For example, intensional definitions list aspects or elements that make up their subject. Some definitions refer to music as a score,