I do not know what it is about #4 and #6, it is like a songbird and puts a chill down my spine. And the echo!! Maybe it's just the way the engineer is working the whistle. I know someone is smart enough to line them all up side by side, and play them like a symphony
Yes, the echo. The way they just trail off is fantastic. The 2021 edition is a favorite, with less background noise to contend with and a little bit of gloom in the morning for ambience.