Tangerine Dream is a German electronic music band founded in 1967 by Edgar Froese. The group has seen many personnel changes over the years, with Froese being the only continuous member until his death in January 2015. The best known line-up of the group was its mid-70s trio of Froese, Christopher Franke, and Peter Baumann. In the late 1970s, Johannes Schmoelling replaced Baumann.

Edgar Froese arrived in West Berlin in the mid-1960s to study art. His first band, the psychedelic rock-styled The Ones, disbanded after releasing only one single. After The Ones, Froese experimented with musical ideas, playing smaller gigs with a variety of musicians. Most of these performances were in the famous Zodiak Free Arts Lab, although one grouping also had the distinction of being invited to play for the surrealist painter Salvador Dali. The music was partnered with literature, painting, early forms of multimedia, and more. It seemed as though only the most outlandish ideas attracted any attention, leading Froese to comment, "In the absurd often lies what is artistically possible." As members of the group came and went, the direction of the music continued to be inspired by the Surrealists, and the group came to be called by the surreal-sounding name of Tangerine Dream, inspired by the line "tangerine trees and marmalade skies" from The Beatles' track "Lucy in the Sky with Diamonds."  Froese was fascinated by technology and skilled in using it to create music. He built custom-made instruments and, wherever he went, collected sounds with tape recorders for use in constructing musical works later. His early work with tape loops and other repeating sounds was the obvious precursor to the emerging technology of the sequencer, which Tangerine Dream quickly adopted upon its arrival.  The first Tangerine Dream album, Electronic Meditation, was a tape-collage Krautrock piece, using the technology of the time rather than the synthesized music they later became famous for. The line-up for the album was Froese, Klaus Schulze, and Conrad Schnitzler. Electronic Meditation was published by Ohr in 1970, and began the period known as the Pink Years (the Ohr logo was a pink ear). But starting with their second album, Alpha Centauri, the group has been a trio or occasionally duo of electronic instruments, commonly augmented by guitar from Froese (or, much later, other musicians as well), and occasionally also other instruments. Of these, drums from Christopher Franke and organ from Steve Schroyder (on Alpha Centauri) or Peter Baumann (on subsequent releases) feature prominently in the band's music during the early 70s. They also started their heavy usage of the Mellotron during this period.

Answer the following question by taking a quote from the article: what is Psychedila and krautrock?
psychedelic rock-styled