Ágætis byrjun ( , A good beginning) is the second album by Icelandic post-rock band Sigur Rós, released on 12 June 1999. Ágætis byrjun was recorded between the summer of 1998 and the spring of 1999 with producer Ken Thomas and became the band's breakthrough album, both critically and commercially. Ágætis byrjun represented a substantial departure from the band's previous album Von, with that album's Cocteau Twins-esque dream pop and extended ambient soundscapes replaced by Jónsi Birgisson's now signature cello-bowed guitarwork and lush orchestration, using a double string octet amongst other orchestral elements.