Headache Machine, the debut album by this gutsy power pop quartet from Austin, Texas, shows abundant promise with melodies, roughly ringing guitars, electricity and a certain nascent stylistic flair. But Sophomore Slump, produced to order by Tommy Erdelyi, is definitely the record to get by these guys. Singer/guitarist Steve Collier’s writing shows marked improvement; the band rushes at his songs with youthful eagerness and the self-confidence of seasoned roadhogs. Crossing an attractive Athens influence, a hint of folk and a dusty Southwestern truth those California cowboys would dearly love to borrow, Doctors’ Mob get onto something good.