There are multiple artists with this name:
1) Mushroom San Francisco-based psychedelic, post-jazz, improv collective with an ever-changing lineup of players founded by drummer Pat Thomas. Their rotating personnel has led to guest appearances by many of their influences, including Gong's Daevid Allen, Soft Machine's Kevin Ayers and Cream lyricist Peter Brown. Notable recent collaborators include jazz trumpeter Eddie Gale, Alison Faith Levy and Gary Floyd.
2) Mushroom is an alias of goa trance artist Marc Hunt. His only release using this alias was "The Fungus Amongus" (1994) released by Magick Eye Records on both CD and vinyl.
3) Mushroom is a house music producer/engineer from Brasschaat, Belgium. He had 3 releases so far, Nu Nu (2004), Topradio The Party Station 6 (2004) and Club Hits 2006 (2005).
4) Mushroom is an IDM/glitch web artist.
5) Mushroom is a German psychedelic trance artist,.
6) Mushroom is a German progressive rock band.
7) Mushroom is an Irish progressive rock band.
8) Mushroom is a Dutch 1970s hard rock/heavy psych band.