soundscape-qt is an open source desktop application to play a mix of sounds, e.g. natural sounds produced by animals or wind and water.
soundscape-qt comes with two example soundscapes. Use mouse right-click in the main window or on the tray icon to access application menu where you can add or remove soundtracks and change their settings.
Use the Quit item from the application menu to finish the application.
Pressing the close window button will just minimize it to the tray.
Freesound is a good source of sounds for your own soundscapes.
Prebuilt binaries for Windows, macOS and Linux are available from the Releases page.
On Linux you may need to install additional packages in order to run the application. Most likely XCB util-cursor module is missing. On Debian-based systems you can install it with
sudo apt-get install libxcb-cursor0
and on RPM-based sytems with
sudo dnf install xcb-util-cursor