Enigmatic Icelandic group Sigur Ros [ tickets ] plays a series of U.S. club and theater dates in March and April to back their critically-acclaimed 2002 album "()."

"()" features eight songs, all of which are untitled. The album's few lyrics are sung in "Hopelandic," a gibberish "language" created by Sigur Ros singer/guitarist Jón Por "Jónsi" Birgisson that "fits to the music and acts as another instrument," according to the band's official website.

Birgisson often plays his guitar using a cello bow, and the band's sound is atmospheric and experimental.

Even the album artwork for "()" is unusual: the jewel case is surrounded by a plastic cover with two parenthesis-like cutouts, and the CD booklet contains 12 blank pages. Fans must go to the band's website to read the album credits.

The unpronounceable symbol that serves as the album's title "can be interpreted as either an emphasis on the album's untitle (the listener is free to make up his/her own title since there is essentially none) or an emphasis on the division of the album, the two semi-circles symbolizing the album's two halves," the band's website explains. "Or maybe it doesn't 'mean' anything."

"()" is Sigur Ros' third album. The band's profile got a huge boost when Radiohead's Thom Yorke cited the group as an influence for Radiohead's critically acclaimed 2000 album, "Kid A."

The band won the first Shortlist Prize for Artistic Achievement in Music in 2001.