"[4] Among the artists the band cited for musical inspiration on Everything Harmony were the Beach Boys, Arthur Russell, Simon and Garfunkel, Curtis Mayfield, and the Left Banke;[5][6] reviewers also noted influence from the Bee Gees, the Byrds, James Taylor, and Teenage Fanclub.

[7] Everything Harmony's early sessions took place in Manhattan's Music Building, which proved unsuitable for recording the album's acoustic ballads.

Campbell added: "when you consider that the album was recorded, produced and engineered solely by the D'Addario brothers, it adds even more weight to the fact that they could create songs that harken back to classics without sounding too derivative".

[12] Ben Beaumont-Thomas of The Guardian opined that the duo "have never mined the past more effectively than on this fourth album", writing that their "biggest touchstone is the beautifully harmonised existential dread of the Beach Boys post-Pet Sounds flop era: rarely has stark despair (one song is called Every Day Is the Worst Day of My Life) sounded so lovely".

[7] Fred Thomas of AllMusic felt that the album has the duo "changing directions yet again, turning the volume down and exploring a more sentimental side of their '70s-informed songwriting style", with its "especially gentle songs" like "Any Time of Day" demonstrating "the band's progression the most".