Task: Question Answering
Input (English): Passage: Audioslave was an American rock supergroup formed in Los Angeles in 2001. The four-piece band consisted of Soundgarden lead singer/rhythm guitarist Chris Cornell and Rage Against the Machine members Tom Morello (lead guitar), Tim Commerford (bass/backing vocals), and Brad Wilk (drums). Critics first described Audioslave as a combination of Soundgarden and Rage Against the Machine, but by the band's second album, Out of Exile, it was noted that they had established a separate identity. Audioslave's sound was created by blending 1970s hard rock with 1990s alternative rock. Moreover, Morello incorporated his well-known, unconventional guitar solos into the mix. As with Rage Against the Machine, the band prided themselves on the fact that all sounds on their albums were produced using only guitar, bass, drums, and vocals.
In its six years of existence, Audioslave released three albums, received three Grammy nominations, sold more than eight million records worldwide and became the first American rock band to perform an open-air concert in Cuba. Audioslave disbanded in February 2007 when Cornell issued a statement announcing that he was permanently leaving the band "due to irresolvable personality conflicts as well as musical differences." The 2007 Rage Against the Machine reunion and tour involving the rest of the band, as well as solo albums released that same year by Morello and Cornell, cemented the supergroup's permanent demise. On January 20, 2017, three days after announcing their reunion, Audioslave performed together for the first time in over a decade at Prophets of Rage's Anti-Inaugural Ball. In the early hours of May 18, 2017, Chris Cornell was found dead in his hotel room in Detroit, at the age of 52, after playing a Soundgarden show. 
Question: What were the two types of rock that created Audioslave's sound?
Output (English): hard rock.