The Doobie Brothers debut album came out in April 1971. They were a 4-piece initially with Tom Johnston, Patrick Simmons, Dave Shogren and John Hartman being the line-up, playing a more country rock sound than they would in the future. It didn't chart and I've always thought it was unfairly overlooked at the time and subsequently. They would play 'Slippery St Paul' from this in their live set for many years.