What you want to do cannot be done.
Not mentioning the fact that as you mentioned, this database format is proprietary and also it cannot be accessed as you like. You cannot query the database for a list of artists or a list of albums. It has not been built for that purpose.
Your Gracenote contact will tell you the same. Eventually, you could buy a data export from Gracenote that has the info you need, but that’s about it.
To find your contact at Gracenote, you could just go through https://www.gracenote.com/support/ and submit a request using your company’s email. We will get your request on the other side and your existing contact should get back at you.
You should rather look at Echonest or MusicBrainz or others that have public APIs that do what you ask.
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solved How to access an offline copy of the GraceNote database? [closed]