Mainstream Nashville country is so helplessly in thrall to songwriting convention that it’s hard to tell decent singers from generic one-hat wonders. Brad Paisley tends to sidle up to a tune, and that relaxed delivery keeps his love songs from becoming unduly sentimental and his funny stuff from elbowing you in the ribs. The title track of his 2003 disc, Mud on the Tires (Arista), for instance, is an invitation to an off-road romp that’s sung so casually it takes several listens to hook you. Paisley’s restraint proves disastrous on the first single from the album, “Celebrity”–essentially a toothless, down-home rewrite of Good Charlotte’s “Lifestyles of the Rich and Famous.” But few other men in mainstream country could make the patronizing “Little Moments,” a series of anecdotes about how cute his honey is when she embarrasses herself, feel so indelibly sweet.