The Nitty Gritty Dirt Band, an American country rock band, has existed in various forms since its founding in Long Beach, California in 1966. The group's membership has had at least a dozen changes over the years, including a period from 1976 to 1981 when the band performed and recorded as the Dirt Band. Constant members since the early times are singer-guitarist Jeff Hanna and drummer Jimmie Fadden. Multi-instrumentalist John McEuen was with the band from 1966 to 1986 and returned during 2001 departing once again in November 2017.

The Nitty Gritty Dirt Band was founded around 1966 in Long Beach, California by singer-guitarist Jeff Hanna and singer-songwriter guitarist Bruce Kunkel who had performed as the New Coast Two and later the Illegitimate Jug Band. Trying, in the words of the band's website, to "figure out how not to have to work for a living," Hanna and Kunkel joined informal jam sessions at McCabe's Guitar Shop in Long Beach. There they met a few other musicians: guitarist/washtub bassist Ralph Barr, guitarist-clarinetist Les Thompson, harmonicist and jug player Jimmie Fadden, and guitarist-vocalist Jackson Browne. As Nitty Gritty Dirt Band, the six men started as a jug band and adopted the burgeoning southern California folk rock musical style, playing in local clubs while wearing pinstripe suits and cowboy boots. Their first paying performance was at the Golden Bear in Huntington Beach, California.  Browne was in the band for only a few months before he left to concentrate on a solo career as a singer-songwriter. He was replaced by John McEuen on banjo, fiddle, mandolin, and steel guitar. McEuen's older brother, William, was the group's manager, and he helped the band get signed with Liberty Records, which released the group's debut album, The Nitty Gritty Dirt Band during 1967. The band's first single, "Buy for Me the Rain," was a Top 40 success, and the band gained exposure on The Tonight Show Starring Johnny Carson, as well as concerts with such disparate artists as Jack Benny and The Doors.  A second album, Ricochet, was released later during the year and was less successful than their first. Kunkel wanted the band to "go electric", and include more original material. Bruce left the group to form WordSalad and Of The People. He was replaced by multi-instrumentalist Chris Darrow.  By 1968, the band adopted electrical instruments anyway, and added drums. The first electric album, Rare Junk, was a commercial failure, as was their next, Alive.  The band continued to gain publicity, mainly as a novelty act, making an appearance in the 1968 film, For Singles Only, and a cameo appearance in the 1969 musical western film, Paint Your Wagon, performing "Hand Me Down That Can o' Beans". The band also played Carnegie Hall as an opening act for Bill Cosby and played in a jam session with Dizzy Gillespie.

Answer the following question by taking a quote from the article: Did they sing with any other groups during this time?
Jack Benny and The Doors.