Task: Question Answering
Input (English): Passage: In early 2005, Frusciante entered the studio to work on his fifth and final studio album with the Chili Peppers, Stadium Arcadium. His guitar playing is dominant throughout the album, and he provides backing vocals on most of the tracks. Although usually following a "less is more" style of guitar playing, he began using a full twenty-four track mixer for maximum effect. In the arrangements, he incorporates a wide array of sounds and playing styles, similar to the funk-influenced Blood Sugar Sex Magik or the more melodic By the Way. He also changed his approach to his playing, opting to contribute solos and allow songs to be formed from jam sessions. In an interview from Guitar World, Frusciante explained how he approached his guitar solos for their album Stadium Arcadium completely differently from those for their previous albums. On Blood Sugar Sex Magik and Californication, Frusciante had a general idea how he wanted his guitar solos to sound. For Stadium Arcadium, almost every guitar solo was completely improvised by Frusciante on the spot. Several reviews have stressed that the influence of Hendrix is evident in his solos on the album, with Frusciante himself backing this up. He also expanded the use of guitar effects throughout the album, and used various other instruments such as the synthesizer and mellotron. He worked continuously with Rubin over-dubbing guitar progressions, changing harmonies and using all his technical resources.Frusciante began a series of collaborations with friend Omar Rodríguez-López and his band The Mars Volta, by contributing guitar and electronic instrumentation to song "Cicatriz ESP" off their album De-Loused in the Comatorium. He also contributed guitar solos on their 2005 album Frances the Mute. In 2006, he helped The Mars Volta complete their third album Amputechture by playing guitar on seven of its eight tracks. In return, Rodriguez-Lopez has played on several of Frusciante's solo albums, as well as making a guest appearance on Stadium Arcadium. 
Question: What is the name of the group that Frusciante provides backing vocals for?
Output (English): the Chili Peppers.