Plain White T's: Tim Lopez (vocals, guitar, piano); Tom Higgenson (vocals, harmonica, piano); Mike Retondo (vocals, melodica, bass clarinet, saxophone, cornet, piano, bass instrument); Dave Tirio (guitar); De'Mar Hamilton (drums). <p>Personnel: Matt Harris (vocals); Johnny K. (slide guitar, Mellotron); Rachel Pine (strings); Brett Anderson (trumpet); Fred Johnson (trombone); Pat Gilroy (piano); William Hamilton (organ); Jon Brion (chamberlin). <p>Audio Mixers: John O'Mahoney; Andy Wallace. <p>Arrangers: Ian Kirkpatrick; Rachel Pine. <p>The plaintive acoustic ballad "Hey There Delilah" launched the unassuming Illinois group Plain White T's into the role of unlikely stars. For their follow-up, it would be tempting for the band to make a whole album of ballads just like that one, but they instead take a minute to try some new things and sharpen their songwriting. Granted, no one will mistake BIG BAD WORLD as experimental, but it's still a more mature Plain White T's that's visible on its 10 tracks. The pretty "Rainy Day" falls as softly as its namesake precipitation, with light sprinklings of acoustic guitar and drums scattered like fat droplets falling from the an awning. "That Girl" is rickety, homespun pop with the flavor of hayride Americana, and they give in to the ballad itch with the quiet Sesame-Street-for-adults "1,2,3,4."