Musically, "B.O.B." is a whirlwind of a track that smacks the listener right upside the head. As André 3000 implores the listener - "who want some? Don't come unprepared" - but it's d--n near impossible to be prepared for the frantic, up-tempo rhythm in this track. Yeah - clocking in at 135 beats per minute - it's probably safe to consider this beat frantic. As Big Boi remembers, "when I first heard the beat, the room seemed to have this glow to it." The beat in "B.O.B." is a far cry from the slow, funky, Southern beats that first made OutKast famous, but in this track André and Big Boi were up for the challenge. André explained to Rolling Stone that, "the sound of the music has changed today because you got kids on totally different drugs. First, everybody was doing the weed thing, and s----t was slower. Now, they on the X, so they want it faster. They want to move. It's this rave energy. The new hippies are rave kids. Songs like 'B.O.B.' are the heartbeat of what's going on with the youth right now." According to A&R man Kawan Prather, "it was a beat and a lot of noise, but they rode the beat so well that it didn't sound foreign or weird."
The funky, frantic drum-and-bass beat is only the start, as the track jumps around from one musical styling to another. Blender characterized "B.O.B." as a track that packs "the past 25 years of music history in five minutes and four seconds...as if several radio stations were simultaneously competing for your ear." The song blends mind-numbing funk, drum-and-bass, gospel, jungle rock, and spacey electronica together into one complete whole. Each of these distinct musical genres makes sense together in "B.O.B." - the song by no means sounds disjointed. The track builds from the beat to a call-and-response hook between André and the Morris Brown College Gospel Choir. He sings, "don't pull the thang out unless you plan to bang," the choir responding with "bombs over Baghdad." André calls out again, this time with, "don't even bang unless you plan to hit something." Once again, the choir responds with "bombs over Baghdad." It's a powerful part in a powerful song. The song then switches gears as it goes from the hip-hop verses to a lengthy guitar solo that sounds oddly similar to Jimi Hendrix's version of the "Star Spangled Banner" at Woodstock. Over this there's some DJ scratches and the gospel choir continues its chant of "bombs over Baghdad." It all wraps up with what is a downright inspired and inspiring chant of "power music electric revival" that sounds more like a praise service than a rap song. And in the end that is probably the most apt way to describe "B.O.B." as a piece of music - "power music electric revival."