By the time he reached stardom in 1976, Bob Seger already sounded like an old man reflecting on a rich past. That’s because he already had a significant past. Some of his early days are assembled on Heavy Music, which collects recordings with his garage band, The Last Heard. A pile-driving Motor City beat supports the feral vocals, serrated fuzztone guitars and reedy organ. In those days, Seger was young, wild and agonized, drawing from models such as Them (“East Side Story”) as well as Highway 61-era Bob Dylan (“Persecution Smith”), soulful balladeering (“Very Few”) and ornate yet energetic psychedelia (“Vagrant Winter”). He even tips his hat to James Brown on the funky-funny “Sock it to Me Santa” and spoofs Jan and Dean with “Florida Time.” Seger hadn’t arrived at his own sound yet, but the diversity of Heavy Music is striking.