Welcome, Anthony! BMR is one of my FAVE Joni songs ever, and hopefully in our time will become the jazz standard it deserves to be. It's been covered 3 times in the past year...
The "boom boom pachyderm" line has been a controversial one around here forever. Some give it a sexual connotation, which I had always associated with it as well. Pachyderm meaning elephant, and referring to his member as being like an elephant's trunk. Others have stated that it's a musical term used in drumming, and that she's simply saying that the guy is a musician and has the ladies hanging around him as musicians tend to have. I'm sure there are other angles as well... Bob NP: Joni, "Court & Spark"