In'R'Voice (birth name Den Kozlov) began his music career in Moscow, Russia. In the late 1980s, he was a fan of the classic industrial bands like Skinny Puppy, Front 242 and Nitzer Ebb. Driven by the innovative sound of industrial music, Kozlov began to experiment with analogue synthesizers. In 1992, he recorded his first tracks on a Studio “Tandem”, which recorded mainly pop musicians, but had very enthusiastic sound engineers. Together they developed the sound of Kozlov's project Inner Resonance Voice. In 1994, In’R’Voice became hugely popular on Moscow's main radio station Maximum and in nightclubs. A year later he received an award for innovations in music from the Ministry of Culture of Russia.

In 1996, Kozlov visited London, and attained early trance music events held by Transient Records (Otherworld Party) and by the label Return To The Source in a Fridge Club and the party label “Pagan” by Tsuoshi Suzuki (Matsury Productions). He recorded collaboration tracks with Tim Healey and Seb Taylor. Kozlov helped to organise concerts in Moscow for the leading trance projects including Shakta, Slide, Quirk, DJ's Baraka, John Phantasm, Mike McGuire (Juno Reactor), and Chris Organic.

In 1999, Kozlov relocated to London, and played alongside James Monro, Blue Planet Corporation, Tim Schuldt, Infected Mushroom, Bumbling Loons, Shakta, Hux Flux and many more. The first full album on Optica Records In’R’Voice, Resonance Metaphizix, was mastered at the Abbey Road Studios in London.

After 2004, Kozlov began to experiment with other styles of music, and recorded “Digital Shamanism” on London's Optica Records, “The Scent of Russian Dreams” on Sphere Records and “Do You Sea What I See” on System Recordings in the US. In 2008, Kozlov founded his own multigenre EDM record label, Kissthesound Records (kissthesound.com), and in 2013 Tech-House label Axiomatic Records (axiomatic-records.com), aiming to release young talented musicians from Russia and Europe producing different trends of music.

Constantly widening his collection of his records, Kozlov has released his music under many project names such as Den Kozlov, Peace Data, Decay Axiomatic, Emotion Code, Karmahacker, Technokitsch, Dive Craft, Shagging Harmonies, T.E.C.H.O., Record Needle Injection, X-Television, Pixelliadians, Psy-Phi Generation, Babnick Enemy, Krolex, S.H.L.I., X-Alt Project, Slake Philter, Overtone Epidemic, Slick Tweak, Levitating Cat, Love In Decay, Eastern Promises, See You Later Oscillator, and Moot.