Munch's (Richard Belzer) use of the word "Falsetto" is incorrect, as a falsetto singer has nothing to do with castration. The correct term would have been "Castrato". A Castrato was a male singer who was castrated before puberty, to enable them to retain their high singing voice. This practice was carried out in Italy from the late 16th century until 1903.
The opening scene was shot in the Exchange Place PATH (Port Authority Trans Hudson) station in Jersey City, NJ. The giant escalator and colorful neon lights are unmistakable. At some point Stabler says: "Here comes the Number 2 train". The NYC subway doesn't stop in Jersey City.
Fin states that the 2 trains run south from Riverdale (where a doctor performs castrations), but this is incorrect. The 1st train runs from Riverdale. The 2nd train runs from the Central Bronx - nowhere near Riverdale.