Question: Friðrik Karlsson is an Icelandic musician and songwriter who contributed to the soundtrack of musical with a book by Nan Knighton and music and lyrics by who?

Context paragraphs:
Fálkar (soundtrack): Fálkar is the soundtrack to "Falcons" ("Fálkar" is the Icelandic word for Falcons), which was directed by Friðrik Þór Friðriksson in 2002.  With 12 tracks, this album contains a variety of Icelandic artists, from Hilmar Örn Hilmarsson, who was in charge of the music composition of the soundtrack, to Mínus, Múm, and Daníel Ágúst Haraldsson (former member of Gus-Gus), among others.

Camille Claudel (musical): Camille Claudel is a musical with a book and lyrics by Nan Knighton and music by Frank Wildhorn, their second musical.  It is based on the life of the real-life French sculptor and graphic artist of the same name.  The musical premiered at Goodspeed Musicals in 2003.

Heart 2 Heart (band): Heart 2 Heart was an Icelandic band.  They represented Iceland in the Eurovision Song Contest 1992 with the song "Nei eða já".  The members of the band were Grétar Örvarsson, Sigga, Sigrún Eva Ármannsdóttir and Friðrik Karlsson.

Selmasongs: Selmasongs: Music from the Motion Picture Soundtrack 'Dancer in the Dark' is the first soundtrack album by Icelandic musician Björk.  It was released on September 18, 2000, by One Little Indian Records to promote and accompany the film "Dancer in the Dark".  In the film Björk starred as Selma Ježková, a Czech immigrant who has moved to the United States.  The album features classical arrangements, as well as melodies and beats composed of sounds from mundane objects, such as factory machines and trains.

Rudolf (musical): Rudolf is a musical conceived for the stage by Frank Wildhorn and Steve Cuden, with a book by Jack Murphy and Phoebe Hwang, lyrics by Murphy, additional lyrics by Nan Knighton, and music by Frank Wildhorn.  Arrangements by Koen Schoots and orchestrations by Kim Scharnberg.  It is about Rudolf, Crown Prince of Austria and his extramarital relationship with Baroness Mary Vetsera.  Their 1889 deaths at his Mayerling hunting lodge apparently were the result of a murder-suicide pact, although historians have debated this explanation.

Friðrik Karlsson: Friðrik Karlsson is an Icelandic musician and songwriter.  He studied classical and jazz/rock guitar and had success with the group Mezzoforte in 1983 with the U.K. top 20 hit, "Garden Party".  He has contributed to the soundtracks of musicals such as Jesus Christ Superstar and Saturday Night Fever and to that of movies such as Evita and Hercules.  His TV work includes accompanying singers Madonna, José Carreras and Tom Jones.  Karlsson has also appeared on albums and singles from Boyzone and Cliff Richard, among others.  Karlsson has moved back home to his native Iceland,after living in London,where he among other jobs worked as a session musician playing guitar in the musical Jesus Christ Superstar.  He has released numerous new-age and relaxation music albums known as "The Feel Good Collection".  In 2014, Karlsson also played as session musician for Kate Bush's first live performances in 35 years, playing guitar for 22 dates.

Saturday Night Fever (musical): Saturday Night Fever is a musical with a book by Nan Knighton (in collaboration with Arlene Phillips, Paul Nicholas, and Robert Stigwood) and music and lyrics by the Bee Gees.

The Scarlet Pimpernel (musical): The Scarlet Pimpernel is a musical with music by Frank Wildhorn and lyrics and book by Nan Knighton, based on the novel of the same name by Baroness Orczy.  The show is set in England and France during the Reign of Terror of the French Revolution.  The story is a precursor to the spy fiction and the superhero genres, where a hero hides under a mild-mannered alias.

Finnur Jóhannsson: Finnur Jóhannsson (born July 28, 1955) is an Icelandic musician, singer and songwriter.  He has been involved in the Icelandic music business for decades and performed the song "Allt eða ekki neitt" in the 2007 Söngvakeppni Sjónvarpsins.

A Little Trip to Heaven: A Little Trip to Heaven is an Icelandic-American noir-inspired drama and thriller film from 2005, directed by Icelandic director of "The Sea", Baltasar Kormákur.  The film is set in the U.S. in 1985 but almost entirely shot in Iceland.  Icelandic musician Mugison composed and performed the soundtrack, except for the song "A Little Trip to Heaven," which is originally by Tom Waits.  Mugison performs the Waits song on the soundtrack.

Supporting paragraphs: Friðrik Karlsson Saturday Night Fever (musical)
Answer: the Bee Gees