Xiaomi
Change Ringtone for Event Reminders auf Xiaomi
Event reminders on Xiaomi phones run through a separate sound channel than calls, messages, or general app notifications. That is why changing your default notification tone in Sound & vibration does not affect calendar alerts, note reminders, or task due dates - they all pull from a dedicated Events sound slot inside MIUI.
To change it, open Settings ➔ Sound & vibration ➔ Events ➔ All ringtones ➔ Choose a ringtone/notification sound. From there you can pick from a short list of Xiaomi-included event tones or browse your own sound files stored locally on the device.
This setting applies system-wide to any app that uses Android's built-in calendar or reminder notification channel, including the stock Calendar app, Notes with due dates, and Tasks. If you only want to silence one specific app instead of changing the sound for all events, adjust that app's individual notification channel instead, since the Events sound covers every app sharing the same reminder category.
One side effect worth knowing: picking a very quiet or short tone can make it easy to miss a reminder buried under other notifications, especially if Do Not Disturb or Focus mode is also active at the reminder time.