Question: Jim Berger and John Rich, have which shared occupation?

Context paragraphs:
Rescue Me (album): Rescue Me is an album by American country music artist John Rich, released in 2001.  Though "Rescue Me" was released before Rich's album "Underneath the Same Moon", it was not recorded until two years later.  Rich was inspired to record the album after he met Katie Darnell, a cancer patient at Monroe Carell Jr.  Children's Hospital at Vanderbilt in Nashville, Tennessee.  Rich was visiting the hospital with a group of songwriters (including future Big & Rich collaborator Big Kenny) to sing Christmas carols for the children when Darnell offered to sing to Rich and Kenny.  Darnell sang "Rescue Me", a song of her own composition, which impressed Rich and Kenny.  They later asked for permission to record the song, which led to an album of the same name.  The album was recorded at Sony/Tree Studios with 30 hours of studio time donated by the location.  Though there was some local interest in the title track, specifically from Gerry House and WSIX-FM, the album was not released on a wide scale.  Prior to her death in 2003, Darnell appeared with Rich on several national TV shows to play her song.

Underneath the Same Moon: Underneath the Same Moon is an album recorded by John Rich.  The album was recorded in 1999, after Rich left from the country group Lonestar and before he joined Big Kenny in the duo Big & Rich.  However, like Big Kenny's 1999 album "Live a Little", this album was not released until 2006, after Big & Rich had released their first album.  Rich also self-released an album in 2001, "Rescue Me", though it was recorded after "Underneath the Same Moon."

Vondur: Vondur (VON dur) was a black metal band from Sweden.  It was made up of members of the bands Ophthalamia and Abruptum, "It" (Tony Särkkä) and "All" (Jim Berger).  The sound could be described as primitive black metal, though rumors have claimed that this was conceived as a joke band.  They released one full-length album, "Stridsyfirlysing", and an EP, "The Galactic Rock N' Roll Empire", both on the now defunct Necropolis Records.  The EP contained two new songs, cover versions of songs by Bathory, Judas Priest, Mötley Crüe and Elvis Presley and a re-recorded version of the song "Dreptu Allur", here translated from the Icelandic to the English "Kill Everyone".

For the Kids (EP): For the Kids is the second Extended Play (or "Six Pak," as referred to on the album cover) by American country music artist John Rich, one half of the duo Big & Rich.  Rich contributed to the writing of three of the six total tracks.  The EP was released on May 17, 2011, coinciding with the release of John Rich's other EP, "Rich Rocks".  Reprise Records released both "For the Kids" and "Rich Rocks".  The songs "She's a Butterfly" and "Rescue Me" were originally recorded by Rich for his 2001 solo album "Rescue Me".

Tony Särkkä: Tony Särkkä (15 December 1972 – 8 February 2017), who went by the stage name It, was a Swedish multi-instrumentalist of Finnish/native American descent who has played in many black metal bands.  He played guitar, drums and bass guitar as well as doing vocals.  He is joined by Jim Berger in many projects.  His projects include Abruptum, Ophthalamia, Vondur, Incision, Brejn Dedd, War and 8th Sin.  He also contributed guest vocals to Dissection's second album "Storm of the Light's Bane", and to Marduk's third album "Opus Nocturne".  He was the founder of The True Satanist Horde in Sweden.

Abruptum: Abruptum is a black metal and dark ambient solo side-project band from Sweden.  It is run by Evil (Morgan Steinmeyer Håkansson) of Marduk, but the band was formed in 1989 by IT (a.k.a. Tony Särkkä).  All (a.k.a. Jim Berger), Ext and Evil joined the band later.  IT was one of the leaders of the True Satanist Horde, part of the Swedish Black metal scene.  Euronymous, co-founder of Mayhem and founder of Deathlike Silence Productions, described Abruptum as "the audial essence of pure black evil".

Rich Rocks: Rich Rocks is the first extended play (or "Six Pak," as referred to on the album cover) by American country music artist John Rich, one half of the duo Big & Rich.  Rich co-wrote all of the songs on the EP with the exception of "Let Somebody Else Drive", which is a John Anderson cover.  On four of the six tracks, Rich is introduced by a friend that is also in the music industry.  Originally slated for a late 2010 release, it was pushed back to May 17, 2011 to coincide with the release of John Rich's other EP, "For the Kids".  Reprise Records released both "Rich Rocks" and "For the Kids".

Live a Little (Big Kenny album): Live a Little is the first solo album by American singer Big Kenny, prior to his joining John Rich in the duo Big & Rich.  Recorded in 1999 for Hollywood Records, the album was not released until 2005, after Big & Rich had released their debut album.  Its release coincided with the release of Rich's previously-unreleased debut album "Underneath the Same Moon", also recorded in 1999 and released in 2006.  Unlike Kenny's work within the country music genre with Big & Rich, "Live a Little" is a mixture between rock and pop.  This album was followed by "The Quiet Times of a Rock and Roll Farm Boy" in 2009 and "Big Kenny's Love Everybody Traveling Musical Medicine Show Mix Tape, Vol.  1" in 2010.

Jim Berger (singer): Jim Berger (born 19 May 1974) is a Swedish black metal singer who goes by the stage name All.  His original project was Abruptum.  He also performed in many side projects, including Ophthalamia, Vondur and War, usually with Tony Särkkä.

John Rich: John Rich (born January 7, 1974) is an American country music singer-songwriter.  From 1992 to 1998, he was a member of the country music band Lonestar, in which he played bass guitar and alternated with Richie McDonald as lead vocalist.  After departing from the band in 1998, he embarked on a solo career on BNA Records in the late 1990s, releasing two singles for the label and recording "Underneath the Same Moon", which was not released until 2006.  In 2001, he self-released "Rescue Me", an album he was inspired to record by a cancer patient named Katie Darnell.  By 2003, he joined Big Kenny to form the duo Big & Rich, who released three albums on Warner Bros.  Records as well as ten singles, including the Number One "Lost in This Moment".  After Big & Rich went on hiatus in 2007, Rich began work on a third solo album, "Son of a Preacher Man", which has produced two more chart singles.  In 2011, Rich released two Extended Plays, "Rich Rocks" and "For the Kids" before re-establishing Big & Rich in 2012.

Supporting paragraphs: Jim Berger (singer) John Rich
Answer: singer