We can set a ringtone for appointments or events on the Xiaomi smartphone, with a choice of selected Xiaomi tones, or any of the pre-installed standard ringtones.

Event reminder sounds work for calendar reminders, notes and tasks.

Android 10 (MIUI 12.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Sound & vibration
Step 3:  Tap on  Events
Step 4:  Tap on  All ringtones
Step 5:  Choose a  notification sound for events
  1. Open the Settings
  2. Tap on Sound & vibration
  3. Tap on Events
  4. Tap on All ringtones
  5. Choose a notification sound for events

Xiaomi Instructions