The 3-chime on the K4 decoder was recorded off of a narrow gauge steamer on the Georgetown Loop in Colorado. If you play it next to a recording of the K4, they are noticeably different. They are also noticeably in the same family (the PRR passenger whistle also being a 3-chime). It is by far the closest of the three whistles on the decoder. It's a shame Bachmann didn't include the B&O 3-chime. It's still not right, but it's the closest in the Soundtraxx library.