The band contrasted the material on the album with the material on its first album, which songwriter Mikel Jollett described as consisting entirely of "sad songs about girls." All at Once, by contrast, contains "only three sad songs about girls." The material features expanded use of keyboards and is louder in many parts, but also contains acoustic songs. All the songs were described as autobiographical except "Welcome to Your Wedding Day," which was penned in response to the Deh Bala wedding party bombing. "All those people died and then everyone was on the news like, 'I don't understand why they don't appreciate our presence,'" Jollett said. "That's not really autobiographical as much as it is about how it's stupid to think people would be thankful for you bombing them."