Good question, and I don't know the answer. It could be just bass, baritone, tenor, but if the "bass" guy isn't singing the fundamental that wouldn't be what I'd consider accurate. In barbershop you have first tenor, second tenor (often carries lead part, sometimes just called "lead" while the other tenor is just called "tenor"), baritone and bass. When I am trying to describe a part I want I often use the terms "near" or "distant" to describe where I am talking about. For instance if I wanted to sing at the next chord note over the lead and for someone else to pick up the next higher one, I might say, "I'll take the near, high harmony and you take the distant, high harmony." It seems to work well with the lady who does most of the harmony with me. I had heard it it described that way from someone else (I didn't come up with it myself), but I don't know that it is commonly used. You could also describe the notes below the lead the same way (near, low harmony).