Question: What is a compilation album of previously unreleased songs and alternate takes recorded 1969–1980 by American singer-songwriter, who was one of the most popular acoustic artists of the decade and one of its best-selling artists?

Context paragraphs:
Scarchives Vol. 1: Scarchives Vol.  1 is a CD and DVD digi-pak compilation from the Finnish band Lordi, released on 3 September 2012.  The compilation contains rare archive materials from Lordi, and was released to celebrate the 20 year anniversary of the band.  The CD contains a previously unreleased studio album recorded in 1997, "Bend Over And Pray The Lord".  The original version of the song, "Get Heavy" (recorded in 1997), and a previously unreleased song entitled "Hulking Dynamo" (from the "Get Heavy" recording sessions in 2002) are included as a bonus track .  The DVD includes a gallery of unreleased songs from 2002; as well as the full video from Lordi's first concert (in Helsinki, 2002), which has an audio commentary by Mr. Lordi.  The DVD was edited by Lordi's former drummer, Tonmi "Otus" Lillman.

Nuthin' but a Gangsta Party 2: Nuthin' but a Gangsta Party 2 is a compilation album released by Priority Records on July 3, 2001.  Like its predecessor, It contains mostly previously released songs along with a few exclusive, previously unreleased songs.  The album peaked at #85 on the Top R&B/Hip-Hop Albums chart.  "Got Ta Hustle", "Make It Happen", and "4 Days In Cali" are all previously unreleased and are exclusive to this album.  The song "Got Ta Hustle" was released as a 12-inch single

Greatest hits album: A greatest hits album, sometimes called a "best of" album or a catalog album, is a compilation of songs by a particular artist or band.  Most often the track list contains previously released recordings with a high degree of notability.  However, to increase the appeal, especially to people who already own the original release, it is common to include remixes or alternate takes of popular songs; sometimes even new material (previously unreleased) will function as bonus tracks.  At times, a greatest hits compilation is the original album release for songs that have themselves been released as a single and charted successfully.

John Denver: Henry John Deutschendorf Jr. (December 31, 1943 – October 12, 1997), known professionally as John Denver, was an American singer-songwriter, record producer, actor, activist, and humanitarian, whose greatest commercial success was as a solo singer.  After traveling and living in numerous locations while growing up in his military family, Denver began his music career with folk music groups during the late 1960s.  Starting in the 1970s, he was one of the most popular acoustic artists of the decade and one of its best-selling artists.  By 1974, he was firmly established as America's best selling performer, and AllMusic has described Denver as "among the most beloved entertainers of his era".

More Grey Hairs: More Grey Hairs is a compilation album by the American rapper Reks, released on March 10, 2009, by6 ShowOff records.  The album contains previously unreleased songs that were cut from Reks' previous album, "Grey Hairs", and other unreleased songs recorded at that time.

Intensities in 10 Cities: Intensities in 10 Cities is the second live album by the American guitarist Ted Nugent, released in 1981 and consisting of ten songs recorded during the last ten dates of Nugent's 1980 tour.  Nugent played 2 or 3 new songs every night on the tour, and told audiences he was recording them for possible inclusion in a new live album featuring all previously unreleased songs.  None of the songs had appeared on any previous Ted Nugent album.  Nugent explained at the time that about twenty previously unreleased songs were played at the beginning of the tour, and at the end the best ten were recorded live rather than in the studio later, because they were well-honed from months of performances and had the extra spark of a live setting.  It was Ted Nugent's final album for Epic Records and the last album to feature drummer Cliff Davies.

The Contrast (band): The Contrast are a guitar power pop band based in Peterborough, Cambridgeshire in the United Kingdom.  They were formed in 1999 by David Reid and have since released five albums on the New York based label Rainbow Quartz and two for Wicked Cool Records.  Since the release of their second album "Wireless Days", their music has been regularly played by Little Steven on his Underground Garage radio show.  Little Steven once described them on air as "One of the best bands on the planet – and England too" and consequently invited them to play the Underground Garage Festival on Randall's Island in 2004.  In May 2007, they released a new album called "Underground Ghosts" (also on Rainbow Quartz) that has since been regularly featured on Little Steven's Underground Garage show.  A compilation of tracks from all of the Rainbow Quartz albums was released in 2007.  This contains new and unreleased tracks and is the band's first release on Little Steven's "Wicked Cool" label.  The band's song "Mystery #1" was featured on a Wicked Cool compilation album, "The Coolest Songs In The World- Vol 2".

Forever, John: Forever, John is a compilation album of previously unreleased songs and alternate takes recorded 1969–1980 by American singer-songwriter John Denver.  It was released posthumously in 1998.

10th Anniversary: Rap-a-Lot Records: 10th Anniversary: Rap-A-Lot Records is a compilation album released by Rap-a-Lot Records to celebrate the label's tenth anniversary.  The compilation contained 11 hits from the likes of the Geto Boys, Scarface and the 5th Ward Boyz, as well as two previously unreleased songs ("Sunshine" by Scarface and "Don't Give No..." by Do or Die) and one song recorded exclusively for the album ("Bring It On").  Former 1 of the Girls member, Nina Creque, daughter of jazz musician Neal Creque, is featured on the previously unreleased "Sunshine" by Scarface.

Live at the BBC (Beatles album): Live at the BBC is a 1994 compilation album featuring performances by the Beatles that were originally broadcast on various BBC Light Programme radio shows from 1963 to 1965.  The mono album, available in multiple formats but most commonly as a two-CD set, consists of 56 songs and 13 tracks of dialogue; 30 of the songs had never been issued previously by the Beatles.  It was the first official release by the Beatles of previously unreleased performances since "The Beatles at the Hollywood Bowl" in 1977 and the first containing previously unreleased songs since their final studio album, "Let It Be", in 1970.

Supporting paragraphs: Forever, John John Denver
Answer: Forever, John