Musically, the sound of Warnings/Promises has been described as college rock and folk rock that strayed from the band's punk rock roots. Woomble said the band attempted to mesh their American influences, such as Superchunk and Hüsker Dü, with acts that they later discovered, such as the Byrds and Buffalo Springfield, adding in elements of country and folk music. Woomble said in contrast to Jones influencing the sound The Remote Part, Warnings/Promises had "more of my influence on it, bringing it into roots and folksy territories." Warnings/Promises expanded on the reflective nature of The Remote Part, showcasing more of an emphasis on acoustic instrumentation, such as acoustic guitars, piano, and string arrangements. Jones stated that the album is "more stripped back and direct" than previous releases, and that it has a sense of "frailty" to it. Discussing the title, Woomble said it relates to "contradictions that make up people. [...] I think we live our lives being promised about things, and being warned about things". He added that the songs dealt with said contradictions and "working your way through them, seeing both sides, understanding, and accepting them".
