These French alt-Muzakers have always been aptly named; like air, their music can be breezy and refreshing even when you suspect there’s nothing IN it. The duo’s fourth album succumbs to their substance-challenged side. The faux-naive stance is merely irritating, the bubblegum track merely cute, the cheese-rock quotient merely cheesy. Robotic voices so ruin the lovelorn lyric to ”How Does It Make You Feel?” that a cameo by Beck (on the techno-folk ”The Vagabond”) feels somber by comparison. As gorgeous as Air’s array of keyboards can be, there’s a thin line between ambient and aimless.