Oppo
Change Notification Sound auf Oppo
On Oppo phones running Coloros, one shared notification sound plays for almost every app that sends alerts, from email clients to social apps. The Phone and Messages apps are the exception, since they use their own separate tone settings and are not affected by this change.
The default notification tone is controlled centrally in the sound settings, not per app. This means you only need to change it once, and every app that relies on the system default will use the new tone going forward.
To change it, go to Tap on Settings ➔ Tap on Sound & vibration ➔ Tap on Notification sound ➔ Set a Notification sound. From the list, pick a preinstalled tone or, if your device offers it, a custom audio file stored locally.
If you want a specific app, like a messaging or email client, to play a different sound than everything else, this system-wide setting will not help. In that case, check whether the app itself has its own notification sound option inside its in-app settings.
Keep in mind that some apps override the system default with their own sound if the app was built that way. If a tone change does not seem to apply to one particular app, that app is likely managing its own notification channel independently.