Which alternative rock band released the 1999 album Ágætis byrjun?

Sigur Rós released the 1999 alternative rock album Ágætis byrjun.

Ágætis byrjun was released in Iceland on 12 June 1999 and later reached wider international audiences. The title is commonly translated as “A Good Beginning.” It was Sigur Rós’s second studio album, following Von, and established the group’s expansive, atmospheric style.

The album features vocalist and guitarist Jónsi, whose singing sometimes uses a bowed guitar technique called a “bow.” Several songs use Icelandic lyrics, while “Olsen Olsen” is sung in a wordless vocal language known as Hopelandic, or vonlenska. The record is often described using post-rock, ambient and alternative-rock terms. Its best-known tracks include “Svefn-g-englar,” “Starálfur” and “Ný batterí.” Sigur Rós formed in Reykjavík in 1994.