• Breathing near six a minute, out longer than in, reliably raises heart-rate variability and eases stress. Every journey here is paced by it.
• A pulse inside the sound draws a clearer response from the brain than a beat made between the ears, so the pulse plays in the sound unless you choose headphones.
• Beats between the ears are heard only up to about 30 Hz and on tones under about 1 kHz; studies of their effects are small and mixed, and whether brain rhythms follow them is unsettled.
• 40 Hz sound makes a measurable 40 Hz response in the brain. Whether that helps health is still being tested; the large trial has finished and has not reported.
• Music before bed improves how people rate their sleep. Sound timed to deep-sleep waves needs a brain sensor; this page has none.
• The tunings (136.1, 432, 528 Hz and the rest) are chosen because they sound good together. None has been shown to work better than another.

The shape of each journey comes from guided listening traditions: setting the day down, humming, a counted descent, a hold, and a counted return. We keep the shape and claim nothing for it beyond what is above.