Needs an update.

The UI is clunky and reminds me of when I used the app on my iPhone 3GS. Heck, look at their blog. The "latest" post is from 2020. In fact, it does not appear to have been thoroughly updated since then. Perhaps the secs have abandoned its development? Anyway, there are likely better and newer apps that have the updated tones and a fresher UI.

Poincare_ about SleepStream 2 Pro