Notification Sounds. Tap short audio files or voice messages and select 'Save for Notifications' to create custom alert tones that sync across your devices – like the 20+ sounds available here.

You can set unique tones for individual chats, or entire groups of chats. Add and manage tones via Settings > Notifications and Sounds or in specific chats.

On Android, tap ➕ > Mute > Customize in a chat header.
On iOS, tap Mute > Customize from a chat’s info page.