They gradually shifted from a traditional extreme metal sound to a more experimental, avant-garde style employing symphonic, world music, and progressive elements.

[5] Their first EP Requiem for the Fools attracted the attention of Norwegian black metal musician and producer Euronymous, who signed Sigh to his label Deathlike Silence Records.

[11] By the end of that decade, the band's lineup solidified with the addition of drummer Junichi Harashima and saxophonist/backup singer Dr. Mikannibal (Mika Kawashima).

[14][15] Their eleventh full-length album, Heir to Despair, was released in 2018 and was noted for its incorporation of instruments and compositional styles from traditional Japanese music.

[16][17] Band leader Mirai Kawashima learned to play flute for this album,[4] and it also incorporates Middle Eastern and Central Asian sounds.