Question: What type of band did a cover of a single that sold two million copies from 1969 to 1970?

full_context: Document 1: The Cult: The Cult are a British rock band formed in 1983. Before settling on their current name in January 1984, the band performed under the name Death Cult, which was an evolution of the name of lead singer Ian Astbury's previous band Southern Death Cult. They gained a dedicated following in the UK in the mid-1980s as a post-punk/gothic rock band, with singles such as "She Sells Sanctuary", before breaking mainstream in the United States in the late 1980s as a hard rock band with singles such as "Love Removal Machine" and "Fire Woman". According to music critic Stephen Thomas Erlewine, the band fuse a "heavy metal revivalist" sound with the "pseudo-mysticism ... of The Doors [and] the guitar-orchestrations of Led Zeppelin ... while adding touches of post-punk goth rock". Since the initial formation of Southern Death Cult in Bradford in 1981, the band have had various line-ups; the longest-serving members are Astbury and guitarist Billy Duffy, the band's two songwriters.
Document 2: The Who: The Who are an English rock band that formed in 1964. Their classic line-up consisted of lead singer Roger Daltrey, guitarist and singer Pete Townshend, bass guitarist John Entwistle, and drummer Keith Moon. They are considered one of the most influential rock bands of the 20th century, selling over 100 million records worldwide and holding a reputation for their live shows and studio work.
Document 3: Voices in the Sky: "Voices in the Sky" is a hit 1968 single by the progressive rock band The Moody Blues, and it was written by their lead guitarist Justin Hayward. It was released as a single in June 1968, with "Dr. Livingstone, I Presume" on the B-side. It was later released on their 1968 album "In Search of the Lost Chord", and was the first of two singles from that album, the other being "Ride My See-Saw".
Document 4: Number 1 Record: Many critics praised the album's elegant vocal harmonies and refined songcraft but "#1 Record" suffered from poor distribution and sold fewer than 10,000 copies. However, "#1 Record" has more recently attracted wider attention, and in 2003 it was ranked number 438 on "Rolling Stone" magazine's list of the 500 greatest albums of all time. "Rolling Stone" magazine also ranked the song "Thirteen" as number 406 on its 500 Greatest Songs of All Time.
Document 5: Taurus (instrumental): "Taurus" is a rock instrumental by American rock band Spirit, originally released on their self-titled debut album in 1968. The track, composed by guitarist/singer Randy California, was recorded in November 1967. It has been alleged that Jimmy Page borrowed the descending guitar figure from "Taurus" for Led Zeppelin's signature song "Stairway to Heaven". Led Zeppelin opened for Spirit in an early American tour, providing the possibility that Led Zeppelin had heard the Spirit song before "Stairway to Heaven" was written. In the liner notes to the 1996 reissue of Spirit's debut album, songwriter Randy California writes:
Document 6: The Sweet: The Sweet (also known as Sweet) is a British glam rock band that rose to worldwide fame in the 1970s. Their best known line-up consisted of lead vocalist Brian Connolly, bass player Steve Priest, guitarist Andy Scott, and drummer Mick Tucker. The group was originally called Sweetshop.
Document 7: Wheel in the Sky: "Wheel in the Sky" is a song by the American rock band Journey, recorded in 1977 and included on their fourth studio album, "Infinity." It was written and composed by Robert Fleischman, Neal Schon and Diane Valory.
Document 8: For What It's Worth: "For What It's Worth (Stop, Hey What's That Sound)" (often referred to as simply "For What It's Worth") is a song written by Stephen Stills. It was performed by Buffalo Springfield, recorded on December 5, 1966, and released as a single on Atco Records in January 1967. The single peaked at number seven on the "Billboard" Hot 100 chart. This song is currently ranked number 63 on "Rolling Stone"' s list of The 500 Greatest Songs of All Time as well as the eighth best song of 1967 by Acclaimed Music.
Document 9: I Don't Need No Doctor: "I Don't Need No Doctor" is an R&B song written by Nick Ashford, Valerie Simpson, and Jo Armstead, first recorded by Ray Charles in 1966. Over the years, it has been covered by bands such as garage rock band The Chocolate Watchband in 1969, Humble Pie in 1971, New Riders of the Purple Sage in 1972, metal band W.A.S.P. in 1986, by metal band Great White in 1987, and by the garage punk band The Nomads in 1989. Styx also covered this song. Humble Pie's version became an FM radio hit and reached #73 on the "Billboard" Hot 100 singles chart. In 2007, John Mayer also covered the song in his live album, "Where the light is" in Los Angeles.
Document 10: Rocky Mountain High: "Rocky Mountain High" is a folk rock song written by John Denver and Mike Taylor about Colorado, and is one of the two official state songs of Colorado. Recorded by Denver in 1972, it went to #9 on the US Hot 100 in 1973. (The song also made #3 on the Easy Listening chart, and was played by some country music stations.) Denver told concert audiences in the mid-1970s that the song took him an unusually long nine months to write. On April 10, 2017 the song was certified Gold by the Recording Industry Association of America for sales of 500,000 digital downloads.
Document 11: Spirit in the Sky: "Spirit in the Sky" is a song written and originally recorded by Norman Greenbaum and released in late 1969. The single became a gold record, selling two million copies from 1969 to 1970 and reached number three on the US "Billboard" Hot 100 chart (April 18, 1970), where it lasted for 15 weeks in the Top 100. "Billboard" ranked the record the No. 22 song of 1970. It also climbed to number one on the UK, Australian and Canadian charts in 1970. "Rolling Stone" ranked "Spirit in the Sky" No. 333 on its list of the 500 Greatest Songs of All Time. The song was featured on the 1969 album of the same name. Cover versions by Doctor and the Medics and Gareth Gates have also made the number 1 spot in the UK.
Document 12: Don't Mess with Doctor Dream: "Don't Mess With Doctor Dream" is a 1985 song by the British band Thompson Twins. It was released as a single from their album "Here's to Future Days", and peaked at No. 15 in the UK, spending six weeks on the chart. Written by bandmembers Tom Bailey, Alannah Currie and Joe Leeway, it is an anti-drug song warning of the dangers of drug addiction. It was the first Thompson Twins single to be co-produced by Nile Rodgers. A promotional music video was made for the single which was directed by Godley & Creme along with Meiert Avis.
Document 13: Doctor and the Medics: Doctor and the Medics are an English glam rock band formed in London in 1981. The group received their great success during the 1980s and are best known for their cover of Norman Greenbaum's "Spirit in the Sky", the group's hit single which reached No. 1 in the UK singles charts. The band currently performs, with a different line-up, as a tribute act to various artists. The group's musical style includes neo-psychedelia, glam rock, new wave and pop rock.
Document 14: Spinal Tap (band): Spinal Tap (stylized as Spın̈al Tap, with a dotless letter "i" and a metal umlaut over the "n") is a parody band spoofing the style of rock heavy metal groups. The band first appeared on a 1979 ABC TV sketch comedy pilot called "The T.V. Show", starring Rob Reiner. The sketch, actually a mock promotional video for the song "Rock and Roll Nightmare", was written by Reiner and the band, and included songwriter/performer Loudon Wainwright III on keyboards. Later the band became the fictional subject of the 1984 rockumentary/mockumentary film "This Is Spinal Tap". The band members are portrayed by Michael McKean (as David St. Hubbins), Christopher Guest (as Nigel Tufnel) and Harry Shearer (as Derek Smalls).
Document 15: Spirits Having Flown: Spirits Having Flown is the fifteenth album released by the Bee Gees. It was the group's first album after their collaboration on the "" soundtrack. The album's first three tracks were released as singles and all reached No. 1 in the US, giving the Bee Gees an unbroken run of six US chart-toppers and tying a record set by The Beatles. It was the first Bee Gees album to make the UK top 40 in ten years (not counting the soundtrack for "Saturday Night Fever"), as well as being their first and only UK No. 1 album.
ground_truth: English glam rock band