Some of the frequencies mentioned are available while in the BetterSleep app to mix with other sounds or written content. The A4 at 440 Hz is highlighted to the chart. For more geeking out, you might have an interest Within this interactive comparison of equivalent temperament vs just intonation https://landenbinrt.qodsblog.com/32358519/the-5-second-trick-for-j-band-frequency-range