Signing to Copro Records in 1998, the band's first major release was the album Lo-Def(inition) Discord, which comprised songs from their three demos with a few new tracks.

The band had more time and money to play with this time, and it is here that the classic et9 sound crystallised – harsh metal inspired by Helmet and Neurosis, mixed with softer textured moments, with Tool-esque dynamics and arrangements, not to mention enigmatic song titles and lyrics (e.g. "Möe=ra (t-talk)", "i nagual eye").

During a break in touring and rehearsing following the release of Arc'tan'gent, Karl Middleton briefly entered the studio to lay down additional vocals on a song called 'unhinged' by the rising post hardcore UK band Landmine Spring.

The song featured on their first full-length album Elephantine, which was released in 2001 via Loudspeaker records, and also lead to Landmine Spring playing on Earthtone9's autumn tour.

All members continued to play in other bands – notably, Karl Middleton joined hardcore supergroup the Blueprint.

On Sunday 30 January 2011, Earthtone9 announced that they will be embarking on a six date United Kingdom tour with The Ocean Collective, Maybeshewill and Humanfly.

Earthtone9 announced that they were searching for supporters through Pledge Music for their new EP For Cause and Consequence that features four new songs which at the time were already in production.

[17][18][19] Guitarist Joe Roberts named bands such as Alice in Chains, Carcass, Faith No More, Helmet, Metallica, Monster Magnet and The Police among his influences.