Knowing each other from film school in Savannah, Muller and Matthews started the project Teen Dreamz in 2013, which acted as a precursor to Boy Harsher. The project consisted of Matthews performing her spoken word pieces and Muller providing a musical backing. Throughout the year, Teen Dreamz's sound became more danceable, as Matthews's vocals developed into a more expressive singing style. The band renamed their project as Boy Harsher in 2014. Boy Harsher released its home-recorded debut EP, Lesser Man in the same year. Following their relocation to Massachusetts, the band recorded and released its debut album, Yr Body Is Nothing in 2016 on DKA Records. After the release of 2017's Country Girl EP, the band formed their Nude Club imprint in 2018, re-issuing their catalog. One of the first releases on Nude Club, "Pain II", is a re-issue of their 2014 single with a remix by The Soft Moon. Their sophomore studio album, 2019's Careful, was backed by an extended reissue of Country Girl as Country Girl Uncut. In that year, a remix album of Careful, titled Careful Remixes, etc. was also released; it featured remixes from techno producers such as Marcel Dettmann and Silent Servant. On April 10, 2020, Muller released his debut soundtrack album, Machine Learning Experiments , which featured original scores composed for two short adult films, Orgone Theory and Hydra. The album was issued on Nude Club.
Boy Harsher is often labeled as a dark wave group, with influences ranging from early forms of industrial to electronic body music. Paul Simpson of AllMusic referred to the band's music as "dark, danceable electro pop" that references synth pop and EBM. He has characterized Boy Harsher's music by its minimal beats and synth textures, as well as by Matthews's dynamic vocals that depict "desire, fantasy, and loneliness." On his review for Careful, Kevin Lozano of Pitchfork listed the band as one of the acts that spearhead the minimal synth scene along with Essaie pas, noting the "brisk drum machineloops, oscillating synths, and Matthews’ haunting incantations" that permeate the album's sound. Lozano has previously described the band as "making coldwave that could turn any space in that quiet town into a seedy nightclub." Michael Lawson of The Skinny thought that the band "straddled the middle ground between melancholic cold wave and regimented synth workouts." Boy Harsher draws heavily from cinema, theatrics and graphic design to tailor the band's visual imagery; Matthews and Muller both have a background in filmmaking. They have likened the band to the movies Body Heat and Lost Highway, latter of which was directed by David Lynch, a professed influence on the band. Matthews has expressed appreciation for various female vocalists, including Nico, Circuit des Yeux, Alison Lewis of Linea Aspera, Chelsea Wolfe and Zola Jesus, whereas Muller named Sleep Chamber, Suicide, DAF and Yello as early musical influences on Boy Harsher. Gearwise, Muller mostly employs synthesizers and samplers, stating that he "tries and borrows as much as he can for recording." On the band's minimal instrumentation, he said: "I’m obsessed with how successful the minimalism is with 80s music. It’s really a masterclass of what can be done with a drum machine and a couple of synths." A "half-functioning" Roland Juno-106 was used extensively on Lesser Man EP; their live set features synth lines sampled into an Akai MPC, as well as backing tracks.
