In the late 1950's PRR I1sa's around Columbus were mostly used as hump and transfer engines. Elsewhere on the Pennsy, where these recording were taken, they were still used on the road. I1's had a very distinctive sound caused by loose drive rod bearings that showed up when they were drifting. It is easily heard on the second piece with an I1 going down hill on Horse Shoe Curve. Recordings by John M. Prophet III from the Ryan Hoover Collection.