I dislike the phrase "track" because it is a symbol of the dehumanization of the theater. The phrase "role" denotes that an actor is creating a character and playing it throughout the performance. In the past, most actors who were not the leads (I was trying to avoid any derogatory terms) would play one or at most two "roles" in a show - and were usually paid appropriately.
Over the past four decades, as cast sizes have shrunk, we get the "track" where one actor delivers a line-or-two here and another few there and another bunch here and the work of the actor becomes just a half-dozen or more stopgaps.
Now everyone is using the phrase because it's "cool" without realizing it actually signifies a cheapening of the industry.
It's like the phenomena of "Von Dutch" hats and sweaters that were popular a while back. I can't tell you how many of my gay friends wore "Von Dutch" stuff, until I pointed out that Kenny Howard (Von Dutch) was a racist and homophobic. Hats usually come off pretty fast after that.
http://www.broadwayworld.com/board/readmessage.cfm?thread=972787#3631451
http://www.broadwayworld.com/board/readmessage.cfm?thread=963561#3533883
http://www.broadwayworld.com/board/readmessage.cfm?thread=955158#3440952
http://www.broadwayworld.com/board/readmessage.cfm?thread=954269#3427915
http://www.broadwayworld.com/board/readmessage.cfm?thread=955012#3441622
http://www.broadwayworld.com/board/readmessage.cfm?thread=954344#3428699