Oppo
Set a Custom Notification Sound auf Oppo
Oppo phones running ColorOS ship with a fixed list of default notification tones. Once you get tired of hearing the same sound for every app, the system offers a built-in way to use your own audio file instead of installing a separate ringtone app.
The relevant function sits inside the sound settings under Notification sound. Selecting Select from files triggers a scan of your phone's internal storage for compatible MP3 files and lists everything it finds.
To set your own tone, go to Tap on Settings ➔ Tap on Sound & vibration ➔ Tap on Notification sound ➔ Tap on Select from files, then choose the file you want and confirm to set a custom notification sound.
This method changes the sound for notifications system-wide. If you only want a different tone for one specific app, check that app's own notification settings first, since some apps let you override the system sound per channel.
Keep in mind that only MP3 files stored locally on the device show up in the scan. Files still in cloud storage or messaging app caches need to be downloaded to local storage first, otherwise the list stays empty.