The experimental nature of the first four albums by Tangerine Dream is breathtaking. For those who appreciate early German electronic abstractionism (Kosmische Musik) it's difficult to top these.Although the Virgin Years (from '74 through '83) are more famous, and soundtracks like Thief and Risky Business put them firmly on the world stage, it was in the "Pink Years" from '70-'73 that the most discerning listeners took notice--especially John Peel at the BBC who gave 1973 Album of the Year to the fourth album, "Atem", an event which led directly to Richard Branson's signing of the band to Virgin.Many prefer this period due to an emphasis on sounds derived more from traditional electric instrumentation as opposed to TD's later reliance on synthesizers, sequencers, and computers -- which is not necessarily better or worse -- just different. There is a wonderfully apt description in the Pink Years' liner notes referring to this music as "the sound of abondoned space stations and dead airlocks...".For many people the excellent 2 disc select anthology called "Sunrise in the Third System- The Pink Years Anthology '70-'73" will suffice.However, for those who happen to prefer this period, "Nebulous Dawn: The Early Years" is a must have due to it's inclusion of all of the first four albums.The aforementioned Pink Years anthology also includes tracks from the long unreleased (and later overdubbed) Green Desert album originally recorded after Atem. So if you buy Nebulous Dawn you may want to buy the "Green Desert" album separately; it's readily available today but was not actually released until 1986 and contained overdubs made in '84.In any case these four albums, "Electronic Meditation", "Alpha Centauri", "Zeit", and "Atem" (plus select bonus tracks) constitute a vital step in the course of modern music.(This was the review I wrote for Amazon 4/13)