What people understand and accept as music varies according to location, historical era, culture and individual taste. The actual definition of music is hotly contested; one definition of music may include only those sounds which are considered "pleasant" by the definer, while another may include any sound produced intentionally by an individual or a group. Other definitions may focus on defining music as a physical phenomenon (in terms of sound), as a psychological phenomenon, or as a social phenomenon. Thus music must contain physical, psychological, and social phenomena, including theory, performance practice, dance, and poetry.
The commonly defined aspects that make up music are:
Timbre is the quality of a sound and varies between voices and musical instruments, which are tools used to produce sound. Pitch is how high or low a sound is, and may be further described as definite pitch or indefinite pitch. Intensity is how loud or quiet a sound is and includes how stressed a sound is. Silence is also often considered an aspect of music, if it is considered to exist. Duration is the only aspect common to both "sound" and "silence", being the temporal aspect of music. The spatial location or the movement in space of sounds may also be an aspect of music.
A musician is a person who composes, conducts or performs music.