Musical style and equipment
Throughout their career, Boris have made deliberate efforts to avoid a strong association with any musical style. In particular, they do not consider themselves a heavy metal band despite frequently being categorized as such. In an interview, drummer Atsuo stated: "Having some kind of preconceived message or theme is very boring to me. It becomes a crutch. Just say what you want to say."
The wide variety of genres used by reviewers to describe Boris's music include experimental music, experimental rock, noise music, noise rock, experimental/avant-garde metal, doom metal, post-metal, drone metal, sludge metal, psychedelic music, psychedelic rock, psychedelic metal, and stoner rock. While they first emerged as a sludge metal band with strong hardcore punk influences, their subsequent releases have employed elements of a wide variety of genres, including drone music, old-school industrial music, ambient music, acid rock, garage rock, shoegaze, dream pop, J-pop, and crust punk.
For example, the band's debut release Absolutego featured a "65-minute track of oozing, slow motion, Melvins-inspired drone rock/metal," while their second release and debut official album Amplifier Worship incorporated psychedelia and jam band influences. Their 2000 album Flood incorporated elements from drone. Akuma no Uta and Pink engaged in different stylistic experimentation, including shoegazing, stoner rock, and post-rock. Vein (2007) was released in "Hardcore" and "Noise" versions, whereas New Album (2011) experimented with electronica and dream pop. The album Noise (2014) featured elements from grunge music.
In the studio, Boris self-records using their own in-house equipment. They use minimal overdubs, recording mostly live. Boris uses many different effects pedals, amplifiers, and other guitar accessories while performing live. Wata uses an E-bow to achieve bow-like sounds or to manipulate feedback; this device is held in the hand, like a pick, but relies on a magnetic field vibration to move the guitar's strings. Wata also occasionally plays an accordion and keyboards in concert.
Takeshi typically plays a double-necked bass/guitar live, which allows him to play both rhythm guitar during the band's lengthier tracks as well as bass guitar during their more traditional tracks, without needing to switch instruments. They also play with extremely low tunings, such as A# standard, to achieve a heavier sound. Takeshi used triple octave tuning for the track "Loveless", from their album No. On some tours starting in 2019, Atsuo switches to a full-time lead singer role and the band makes use of a touring drummer.
