Huawei
Set a Custom Notification Sound auf Huawei
Every EMUI installation ships with a short list of built-in notification tones, and after hearing them a few hundred times they tend to blend together. The system does not limit you to that list. EMUI can also use any audio file already stored in the internal memory of your phone as a notification sound, including tracks copied over from a PC or downloaded directly on the device.
The setting lives inside the sound menu rather than the notification menu, which is why it often goes unnoticed. Open Settings ➔ Sounds & vibration ➔ Notification sound ➔ Music on device and select any file saved locally on the phone. EMUI then treats that file exactly like a built-in notification tone.
Keep in mind this changes the default notification sound for the whole system, not for a single app. If you only want a different tone for one app, such as a messenger or email client, check that app's own notification settings first, since many apps override the system default with their own sound picker.
If no files appear under Music on device, the phone either has no compatible audio stored locally or the format is not supported. Standard MP3 or OGG files copied to internal storage are usually recognized without any conversion.