The Auran F7's sound harsh indeed. If you were to put a GP7/9 enginesound into one, it would be a bit more authentic. Still, there is not a proper EMD 567/645 Roots-blown 2-stroke sound for Trainz content. I did not hear these Roots-blown 2-strokes pulling grades in coastal California as they only operated on flat, low land there. I could hear them rev though as the Geeps, and often SW1500's, were doing ESS PEE road switching duty by serving customer freight sidings. I would hear them grunt upon acceleration under load. I rode the SP passenger service from San Francisco to San Jose. Geep 7's or 9's did the power on those local commuters. Then in late 1985, CalTrain took over and F40PH's put the old SP gray nose-bleed Geep workhorses out to pasture.
I could hear the Roots blower whine on the train. The 2-stroke diesels had an awesome chug. Sounded like a Frigidaire Jet Cone Action washing machine also made by General Motors like the EMD locomotives. General Motors always had awesome sounding machinery to even include Chevrolet air-cooled Corvairs. An EMD 2-stroke Roots was the definite diesel loco sound for my ears. EMD 567 actually switched America from steam to diesel.
We've got nothing but grades here in New England except for the old Eastern Railroad between Boston and Portland, Maine and the lines run by the New Haven on the Southshore. The B&M was a poor railroad after WWII. The Great Depression took whatever money they made, after coming out of the 1916 bankruptcy in 1922, caused by JP Morgan pulling every cent out of them during the Panic of 1916. Then post WWII, industry was offshoring or moving away while Patrick McGuiness, who also ran the New Haven, was sucking any kind of cash out of the company and put them into Chapter 11 again in the late 50s or early 60s. The New Haven didn't fare much better under McGuiness.
With their finances on the line, they ran with whatever they had. You'll find old Alco RS-3s, S3s, GE U-boats, and GP7s, and GP9s pulling freights. Sometimes old former passenger F-units A and B or just B-units were thrown in there too.
For a while, they resurrected and ran GP7s with steam heaters on their commuter trains during the early 80s. The old Budd Liners were dying left and right, after putting in well over 45 or more years of heavy service. These were replaced eventually by FP10s, rebuilt E-units from the Paducah Shops painted in maroon, silver, and yellow. We affectionately called those Easter Eggs because of the color scheme. These pulled depowered Budd Liners were turned into passenger cars with a few with cab-controls still in place for use as cabs for push-pull service.
Eventually, the FP10s, were replaced by F40PHs and a rebuilt variant of those is still in operation. These pulled Pullman commuter cars initially followed by Messer Schmidt commuter cars and later Horizon cars. Today, they're still pulling Horizon cars and Rotem double-deck cars.
