When Voice Memo synchronization is activated on iCloud, your recordings are seamlessly transferred to the iCloud platform, utilizing your Apple ID credentials for this process. It's crucial to note that the data synchronized to iCloud does not constitute a backup stored within iCloud. In the event that you decide to alter your Apple ID on the device, a notable consequence follows: the Voice Memos data previously synced to iCloud will be purged from your device. This removal persists until you re-establish a connection with the device using the original Apple ID associated with the Voice Memos in question. This underscores the importance of maintaining consistency with your Apple ID to ensure the preservation and accessibility of your synchronized Voice Memos data on iCloud.
What does iCloud back up? - Apple Support
iCloud backup doesn’t include information that is synced and stored in iCloud, like Contacts, Calendars, Bookmarks, Mail, Notes, Voice Memos, shared photos, iCloud Photos*, Health data, call history, and files you store in iCloud Drive.
*-If you had turned on iCloud Photos, your content is automatically stored in iCloud.
- WARNING: If you delete the iCloud backup for your current iOS or iPadOS device, iCloud stops automatically backing up the device.