From 2004 to 2007, Mono signed to Temporary Residence Limited, released two more studio albums, Walking Cloud and Deep Red Sky, Flag Fluttered and the Sun Shined (2004) and You Are There (2006), and toured worldwide in their support.

Their most recent effort, Nowhere Now Here was released on January 25, 2019, through Pelagic Records, and was produced by the band's longtime friend Steve Albini at Electrical Audio, Chicago.

The band have cited a variety of experimental, avant-rock and classical music artists as inspirations but stated that their aim is to transcend genre, rejecting the post-rock label which has often been applied to them.

Mono's sound is characterised by the lead and rhythm guitars of Goto and Yoda respectively, both of whom make extensive use of reverb, distortion and delay effects.

In January 1999, Tokyo native electric guitarist Takaakira "Taka" Goto began composing music and spent the remainder of the year searching for other musicians with which to form an instrumental rock band; eventually recruiting long-time friend and fellow electric guitarist Hideki "Yoda" Suematsu on rhythm guitar.

The band spent the bulk of the year composing more music and performing at various houses around Tokyo, in the neighbourhoods of Setagaya, Shimokitazawa, and Shibuya.

The band, Onda, and several notable members of the New York experimental music scene (including DJ Olive, Jackie-O Motherfucker, and Loren Connors) remixed One Step More and You Die.

The album, titled New York Soundtracks, was released in February 2004 on Human Highway, Mono's own record label, and a successor to Forty-4.

The album, titled Walking Cloud and Deep Red Sky, Flag Fluttered and the Sun Shined was released in April 2004 on Human Highway in Japan, and on Rykodisk in Europe and Temporary Residence Limited in the United States later in the year.

The band also spent 2005 touring Asia, America, and Europe composing music, and eventually returning to Electrical Audio Engineering in February and September to record their fourth studio album with Steve Albini.

In February 2007, American webzine Somewhere Cold voted their split with World's End Girlfriend Palmless Prayer / Mass Murder Refrain No.

In October 2006, the band returned to Electrical Audio Engineering and recorded a four-track extended play, which was released in April 2007 as part of Temporary Residence Limited's Travels in Constants series, titled The Phoenix Tree.

In November 2006, the band released a two-track extended play titled Memorie dal Futuro through Vinyl Films, and also contributed a track to a Temporary Residence Limited compilation album, Thankful.

In 2008, the band took a year-long break from touring, spending the time composing new music and playing a handful of shows throughout the year, including an appearance at All Tomorrow's Parties in Somerset, England, curated by Explosions in the Sky in May.

Mono returned to Electrical Audio Engineering in June and November 2008 to record their fifth studio album, Hymn to the Immortal Wind, which was later released in March 2009, and followed by a year-long tour of America and Eurasia.

The band played a ten-year anniversary show at the Society for Ethical Culture Hall in New York, United States on 8 May 2009, accompanied by the 24-piece Wordless Music Orchestra.

[8] On December 9, 2017, they announced via their social media pages that Yasunori Takada (drum kit, glockenspiel, synthesizer), who has been a member since the start, will leave the band due to "personal reasons."

[18] Although Mono's musical style has developed throughout their career, it has primarily been characterised by dynamic, guitar-based instrumental soundscapes, the majority of which are composed by lead guitarist Takaakira Goto, in an attempt to channel and express the emotions of joy and sorrow.

[19] The band's style of music originally featured elements of minimalism and noise, and later developed to integrate more complex, orchestral arrangements and instrumentation.

[28] When recording their music, the band has always played live in the studio and, from 2004's Walking Cloud and Deep Red Sky, Flag Fluttered and the Sun Shined to 2009's Hymn to the Immortal Wind, worked with Chicagoan recording engineer Steve Albini, whom they feel accurately captured a live band's "raw emotion to [magnetic] tape.