How do I download my iTunes Match library to consolidate Music libraries?

There is only one library. You can't have multiple librares. If you are subscribed to iTunes Match and have Sync Library turned on in the Music app settings then anything in the iCloud music library is made available on the device or computer being used and anything on the device is then uploaded or matched and added to the iCloud music library.

click here ➜ Use Sync Library with your Apple Music subscription - Apple Support

Basically there should be no reason your iTunes Match library is separate to your local one unless its under a different Apple Account, and then the only way to consolidate this, would be to sign in to the account that holds the iTunes Match library, download the music and then copy it onto whatever other computer or device has your other library.

mkmcfr wrote:

Thank you for your reply.

I only have one Apple account, although I have changed the sign-in name,...

This may be the salient piece of data. Your iCloud Music Library is attached to your Apple ID. Changing the sign in name (email address I assume) may have a negative impact here.

Hold down Alt/Option as you launch Music and create a new empty library, e.g. at ~/Music/Cloud, then enable Sync Library. All your content that Apple recognizes as being part of your iCloud Music Library should be shown once the library has synchronized. Do you see what you want to see, or only a limited selection of purchases? Make sure View > Only Downloaded Music is not checked.

Ideally you would have downloaded anything that was only in the cloud before making a change to your Apple ID. You should also maintain a complete offline backup of everything in case of accidental removals from the live library. If this was a relatively recent change your content may still be associated with the old email address. Reach out to Apple Support and ask for their assistance.

tt2