Koala keeps your songs, samples and settings in its own folder, which is usually
/Android/data/com.elf.koalasampler/files/songs
Getting to it from your phone
Newer versions of Android hide that folder from file manager apps, so Koala has a button to open it for you. In Koala go to SETTINGS, then GENERAL, and press OPEN next to “Koala folder”. That opens the folder in your phone’s Files app, where you can copy, share or delete files.
You’ll also see “Koala” in the list of places to pick a file from whenever you tap the upload / attach button in another app (Google Drive, Gmail, WhatsApp…).
Back up your songs!
That folder belongs to the app, which means Android deletes it when you uninstall Koala.
So every now and then, copy your songs somewhere safe. The easiest way is to open Google Drive, tap +, then Upload, pick “Koala” from the side menu and choose the songs you want to keep.
And please, never uninstall Koala to fix a problem or to get an update - write to me instead.
From a computer
You can also get at the folder over a USB cable. On Mac, Google make an app called Android File Transfer which will let you access it. On Windows, you should be able to access it in Explorer.