Progressive rock, also known as prog rock or prog is a subgenre of rock music, which became popular in the United Kingdom, with subsequent development in Germany, Italy, Chile, Argentina, Spain and France during the mid and late 1960s. and 70. It developed from psychedelic rock and originated, like art rock, as an attempt to give more weight and artistic credibility to rock music. The bands abandoned the short pop single in favor of Instrumentation and composition most frequently associated with jazz or classical music in an effort to give rock music the same level of musical sophistication and critical respect.3 Some songs were replaced by musical suites that often spanned 20, 30 or even 40 minutes long and contained symphonic influences, extended musical themes, lyrics with philosophical-esoteric content and complex orchestrations
The genre is known for its distinct mellotron sound and constantly changing time signature.