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 record was produced on a budget of £500. Their harshest and noisiest recording, it quickly grabbed the attention of the British rock press, with favourable reviews in Terrorizer and Metal Hammer and a five-star rating in mainstreammodern rock magazine Kerrang!
After extensive touring, ...Discord was followed in 1999 by Off Kilter Enhancement. Again it was a critical success, but commercial recognition was limited. 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"). Barely a year later, after the departure of original bassist Graeme Watts, the band delivered their third album – voted 16th best album of 2000 by Metal Hammer. It was described by et9 as the first record they were truly happy with, having for the first time not been rushed in the recording process.
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.
Hopes were high for an American record deal, and it seemed obvious to most that the climate of US radio at the time—very focused on the dominant nu metal sound—could accommodate the cleaner side of earthtone9's output. But, ultimately, apart from some minor distribution of their existing material, all attempts fell through. They lost Hutchby (due to a mysterious skiing accident), and after struggling through for a couple of years, the band announced their dissolution in early 2002. After their farewell tour their umpteenth rejected demo saw release as the Omega EP, hinting at a more melodic direction.
In 2004, hi-point (rem), which was a remastered version of 2000's first EP hi-point, was released.