Question: What American is described as one of the most innovative and diverse rock musicians of his generation and released one of the earliest double albums in rock music?

<P0-S0> Alternative rock (also called alternative music, alt-rock or simply alternative) is a style of rock music that emerged from the independent music underground of the 1980s and became widely popular in the 1990s. <P0-S1>  In this instance, the word "alternative" refers to the genre's distinction from mainstream rock music. <P0-S2>  The term's original meaning was broader, referring to a generation of musicians unified by their collective debt to either the musical style or simply the independent, DIY ethos of punk rock, which in the late 1970s laid the groundwork for alternative music. <P0-S3>  At times, "alternative" has been used as a catch-all description for music from underground rock artists that receives mainstream recognition, or for any music, whether rock or not, that is seen to be descended from punk rock (including some examples of punk itself, as well as new wave, and post-punk). <SEP> <P1-S0> Freak Out! <P1-S1>  is the debut studio album by the American rock band the Mothers of Invention, released June 27, 1966, on Verve Records. <P1-S2>  Often cited as one of rock music's first concept albums, the album is a satirical expression of frontman Frank Zappa's perception of American pop culture. <P1-S3>  It was also one of the earliest double albums in rock music (Bob Dylan's "Blonde on Blonde" was originally scheduled to precede it by a week, but its release was delayed until more than a month later), and the first 2-record debut. <P1-S4>  In the UK the album was originally released as an edited single disc. <SEP> <P2-S0>  His work was characterized by nonconformity, free-form improvisation, sound experiments, musical virtuosity, and satire of American culture. <P2-S1>  In a career spanning more than 30 years, Zappa composed rock, pop, jazz, jazz fusion, orchestral and "musique concrète" works, and produced almost all of the 60-plus albums that he released with his band the Mothers of Invention and as a solo artist. <P2-S2> Frank Vincent Zappa (December 21, 1940 – December 4, 1993) was an American musician, composer, activist and filmmaker. <P2-S3>  Zappa also directed feature-length films and music videos, and designed album covers. <P2-S4>  Publications such as "Ultimate Classic Rock" and "The Independent" have described him as one of the most innovative and stylistically diverse rock musicians of his generation. <SEP> <P3-S0> A double album (or double record) is an audio album which spans two units of the primary medium in which it is sold, typically records and compact disc. <P3-S1>  A double album is usually though not always released as such, because the recording is longer than the capacity of the medium. <P3-S2>  Recording artists often think of double albums as comprising a single piece artistically; however, there are exceptions such as John Lennon's "Some Time in New York City" and Pink Floyd's "Ummagumma" (both examples of one studio record and one live album packaged together) and OutKast's "Speakerboxxx/The Love Below" (effectively two solo albums, one by each member of the duo). <P3-S3>  Another example of this approach is "Works Volume 1" by Emerson Lake and Palmer, where side one featured Keith Emerson, side two Greg Lake, side three Carl Palmer, and side four was by the entire group.